Been told for YEARS I needed to play this game. OK, it's been installed and it turns out I did play for a few hours 3 years ago, though I do not recall it.

I have installed CO8 and Temple+; along with the Portrait Pack off Nexus Mods and verified the pack works and the portraits are available.

OK...what do I NEED to know going into this game? :)

you have most likely been misled. If you didn't forget to activate CO8 via its launcher then you're all set.
I'd ditch the pack but that just me. That's it a terrible unbalanced unfinished bugfest with a lazy patchy (to put it mildly) story (or more correctly almost complete lack thereof). Thankfully it's rather short. And the fact that having the battles turn-based wouldn't by itself automagically make them better than the haphazard Infinity Engine counterparts...

But do not fret! It has one of the best looking pre-rendered backgrounds / models / animations amongst all isometric RPGs or any game for that matter.

Also has tons of potential and good ideas and stuff but to fulfill it this game has to be redone from the ground up - no community patching and hacking gonna save it.

As for playing it - it's a 3rd ed of AD&D and IMO much better for a CRPG that the 2nd. It feels so too, but with the game being this lame/botched and this short with a level cap of whole 10 lvls it's somewhat a basic demo of that fact.

Pro-tip - sorcerers (IIRC that's the mage class that can cast a number of ANY spell at a given level rather than a prepared set) >>>>> conventional 2nd ED mages. Sorcs own this game, esp with the Fireball. Did I say it's an unbalanced mess? You don't need a thief to complete the game and while for the first time maaaaybee you might want to go with one, but really two sorcerers make your party a powerhouse with two magic spitting walking turrets.

PS Even if you chose the CO8 package without the fan made content (correct choice IMO)... It still has fan made content and it's quite prominent - including voice overs and all the bells and whistles and all the brass.

Some things to note about creating/building spellcasters:
* Each spellcasting class has one ability score that governs their spellcasting. For Wizard it's Intelligence; for Clerics and Druids, Wisdom; for Sorcerers and Bards, Charisma.
* To cast a spell, you need to have at least 10 + the spell's level. Hence, you absolutely *need* at least 15 in the ability score by level 9/10 to cast 5th level spells (the highest level available in the vanilla game), and if the stat is less than 10, the character is not viable at whatever their role is supposed to be. You only get 2 stat increases during the game, each of which is only 1 point to 1 stat. (The scarcity of stat increases is one thing I don't like about D&D in comparison to game's like Wizardry and Bard's Tale, where initial stat rolls are less permanent.)
* Multiclassing spellcasters is not a good idea. Don't multiclass with spell casting classes unless you really know what you're doing.

Edit: Add stats needed for Druids and Bards. (Yes, Bards need Charisma, not Intelligence, for spellcasting.) That's assuming the Sorcerer has at least 13 Charisma (yes, Charisma, not Intelligence), and that the player thought to pick the spell Fireball. (I'd recommend at least 15 Charisma to get 5th level spells.)

Thing is, if the Sorcerer is created with low Charisma, then you just created a forever useless character, and I see that to be a serious flaw in the system. Still not without issues, of course, like how a character creation mistake can permanently cripple a character, making the character non-viable. (This sort of thing is one reason I don't consider AD&D and D&D (at least through 3.5e) to be good systems for CRPGs.)

It has been a few years since I last played. I never did play with the Co8 extension although I did try their Keep on the Borderland expansion until a restore save bug caused me to quit.

What I remember from the beginning of the game is that there a lot of walking around Hommlet quests that you can do to build experience before you ever have to venture out to have combat.

Also ranged weapon ammunition in Hommlet seemed to be very constrained. So if you build a party around the construct of Druids casting Entangle and peppering the monsters stuck in minefield this may not work so well until you find the other settlement.

Be wary of accepting NPCs into your party. They steal all the best loot. Be even more wary of marrying an NPC. They are even bigger thieves and you can't eject them. I confess to marrying one in order to get a very nice early magic sword and then just had my party stand idly by while the sole goblin in Hommlet killed her.

Ultimately felt guilty about that act and restarted the game and just avoided the whole marriage issue.

the 3.5 ruleset is IMHO, the worst thing that ever happened to DnD. (short of Hasbro obtaining the rights) With the variouos FEATS, in a game with programmed encounters already in place, select the wrong FEATs and you can cripple a PC. It's why I couldn't stomach PF:KM. That, and starting stats become critical SO..Imma cheat the starting stats by bumping the pt buy to an absurd lvl, though not enough to go 18 down the line. Imma cheat, but geebus. Even *I* have my limits.

As I understand it; vanilla ToEE was an unplayable bug fest with a lvl cap of 10, so a spell cap of 5th lvl. CO8, rasies the lvl cap to 20, so it also adds spells to lvl 9 or 10.

As for activating: Yes, I activated CO8, then installed Temple+ and activated it. I have to use the T+ launcher, for the changes in it to take place. (Modified at start pt buy, modified starting party, etc.) I DO see, the CO8 starting shop, launching form the T+ launcher so...I am "assuming" the CO8 content is present in game.

The feat mechanic is present in 3.0 as well. If you're going to say a specific version of D&D is the worst thing to happen, you should choose the first version that added it. 3.5 didn't make any major changes (though there are some minor changes, including some I disagree with).

So, really you should be criticizing 3.0, not 3.5, here.

(And, of course, stats that change very little (if at all) has been the case since the beginning.) Thing is, unless you're playing content that wasn't originally in the game, due to the way XP gain in 3.5 works, you're not going to be able to level up much past 10, as enemies will eventually stop giving XP.

(Although it's not as bad as 3.0 where the party's average level was used to calculate XP. This means that adding a new level 1 character would give everyone else more XP. Icewind Dale 2 is like this; this combined with the fact that the game allows multiple level ups at once (unlike ToEE, which will take away XP except for 1 less than you would need to gain 2 levels) allows for some rather perverse strategies that ruin game balance by giving you too many levels; even worse, this applies if you add a new character and don't cheat them up to your party level. When you need to use a cheat to keep the game from being too easy, you know something is wrong here.)