Okay, I have the amulet, so the trolls aren't bothering me. However, I'm also accutely aware that my melee-based Guardian is going to have a tough time with the Ylsids (sp?) later on...
My question is: should I forgo being friendly with the trolls in order to reap their xp? Are they worth a lot?
Thanks for the assistance.

Trolls are worth 100 XP each, which is a good amount for such an easy enemy. The trolls on level 5 are of no significance; you can kill them without affecting your standing with the trolls back on level 3.
If you're in the mood for a bit of goblin genocide, you can kill off everyone in the goblin kingdom with no consequences after completing The Mysteries of Finance (be sure to complete Cooking for Goblins first); completing this quest will make the goblins your enemies (although it will not affect the goblins on other levels). As well as getting 500 XP for finishing this quest you can get hundreds more by killing them, and you can earn thousands of gold by robbing their treasury and the gem chest in the throne room if you haven't already.

Cheers dude!! Those links were great, too. Thanks.