Here http://www.camagna.net/g3mirror/index.html is a mirror for the G3 Mods while they work on the site.
The Spellhold links are still valid.

I've tried using these mods - both give an error. The first one says my version is too old or too new to be installed, the second fails because the first is 'located' but not complete

I'm sure it didn't. Come on, tell us what it really said.
Or better yet, run setup-widescreen.exe again & take a screen shot of the error message.

tried to use this mod widescreen.exe so it wouldn't be a tiny screen in the middle of my big screen. keep getting

ERROR: Unable to find DIALOG>TLK in:
dialog.tlk

Please run this program in your Infinity Engine game directory.

FATAL ERROR: Failure<"Unable to find DIALOG.TLK">

if i knew this was some garbage i was gonna have to mod and troubleshoot to even play correctly, i wouldn't have payed money for it. When it says "compatible with windows 8" I expect it to actually be compatible with windows 8. maybe i'm setting the bar a little high.

I had no trouble at all installing the game with the 3.05 version of the widescreen fix. Did you check to see if your game install included the file "dialog.tlk"? Mine does. The widescreen mod finds specific files in the game install and modifies them in order to work--if it can't find the files it needs to modify, then of course it won't do any good to run the widescreen mod, so it bails. The file dialog.tlk is located in the root directory of the GOG install. The problem, whatever it is, is on your end--it's always good to be able to pin down the source of your problem.

BTW, it runs beautifully under my Win8.1x64 install. You should definitely reinstall the game, and if dialog.tlk doesn't show up again, then you should re-download the game from Gog because that file is definitely supposed to be there.

Also, a very important WeiDU mod that the Gog guide unfortunately makes no mention of, but which I (and I'm betting a lot of people) need, is the PST-ddraw mod, which can be found here. This mod was essential for me in running the game under 8.1x64 @ 1920x1200 full screen @ 32-bits of color depth, HD 7850 2GB/Catalysts 13.12 WHQL. When the mod runs you should select "force Direct Draw emulation"--without this mod the screen and mouse cursor were so jerky and uncontrollable that I couldn't really play the game at all. This mod corrected the problem perfectly.

I had forgotten how much of a gas this game is...!....;)