Bookwyrm627: Get the vase quest from Bill Lasker in the Erathian Sewers; this is the promotion quest from Thief to Rogue. The vase is on the mantle above the fireplace in Markham's Manor in Tatalia. Remember to deliver Parson's Letter and get the Quill from Markham before opening the side doors in the first room of Markham's Manor.

If you go Dark Side, you can't get the Spy quest. Once you commit to the Light Side, talk to Bill Lasker again after you've become a Rogue and he'll give you the quest to become a Spy.

The Tunnel to Eofol leads to the Land of the Giants. Once you access LotG, there is a small shrine that serves as a portal to Harmondale; once you access this shrine from the LotG side, the Harmondale shrine becomes active and will teleport you back.

The temples in the Pit and in Deyja will bring dead characters back as Zombies. I don't remember how to fix this condition short of killing them again (or something similar) and using a different temple. I'm surprised temples in other regions won't cure the Zombie status. If you need to kill a particular character, you can have everyone you want to survive drink a water breathing potion and then go stand in a lake until the victims finish drowning.

To steal, first make sure your character with the highest Stealing skill is active (don't forget to account for the expert/master/GM bonus). Then hold down the Control key and left click on who you want to steal from or what you want to steal (in a shop). Anything you steal can't be sold, so don't bother stealing things you won't use. Honestly, this skill is a waste of skill points; the two times it could be used to help complete a quest, there are more expedient ways to get the item you need (like just killing the item holder).

macAilpin: The temple in Erathia cures "Zombieism." Maybe others but that's the one I use with Town Portal.

Bookwyrm627: You're welcome.

MacAilpin has offered a solution for zombieism. I haven't dealt with that problem in so long that I don't remember the solution, so try his idea before you try mine.
A quick google search turned up this thread. Maybe your character is healed of being a zombie, but a bug or something caused the portrait to stay stuck.
http://www.celestialheavens.com/forum/10/4665

As for the vase, check the attached picture. The vase looks like part of the scenary; you have to click on the actual vase (circled). The picture in the Haunted Mansion functions similarly: it looks like part of the mansion until you click on it, at which point you get the item. Wizard Eye won't help you find either one, iirc. Make sure you aren't low on hp when you grab the vase...