Well - generally for arcane magic users in situations like this I would fully recommend the "Tenser's Transformation (spelling?)" spell.
Try and see if you can get ahold of some scrolls of this spell, and it will make your "life" a whole lot easier.
I can't remember how to beat him as a wizard withouth said spells, but summons of any kind would be helpfull (especially Morderkins Sword (spelling?)) if he is completely immune to all magical damage types (fire, cold, acid, lightning).
I think it is possible to talk him into you "looting" the corpse of his Master. But as far as I can see, it requirs successfull insight and persuade rolls in the convesation to convice the Golem.
By the way: I've added a spoiler tag to your thread title to avoid people getting accidently spoiled.
