9th level Wizard?

Okay.

The Tomb of Horrors is primarily about traps... and a Wizard has ways of dealing with them better than a rogue.

Build Steps:
1) Your 9th level feat goes to the Elemental Summoning Reserve Feat (complete Mage).
2) One of your feats goes to a direct damage reserve feat - Fiery Burst is probably best for this purpose (take at 3rd or with your Wizard bonus Feat at 5th). Your main goal on this is to find the one with the most range.
3) Know Permanency.
4) Use Permanency on Detect Magic (or, if you can swing your caster level high enough to pull it off, Arcane Sight).
5) Know Terran (language of earth elementals).
6) Get two wands: Invisibility, and Spectral Hand (both 2nd level spells).
7) Prepare some spells to power your two reserve feats (and never cast them. Ever).

In the Tomb:
1) Watch everything for magic (hence Permenancy). If you see something magical that isn't an item (and, to be safe, even if it is), call a halt, and zap it with Fiery Burst until it's not magical anymore.
2) Nobody touches anything. At all. Except maybe the floor (and there's ways around that - bat familiar, and Imbue Familiar with Spell Ability for Floating Disk - Bat flies with good manueverability, floating disk follows, you ride on floating disk).
3) Every round you're not in an actual battle, and you don't see any unexpected magic, you do the same thing: Summon an Earth Elemental, send it running along your intended path of travel. If it springs a trap, call a halt, and send the elemental by repeatedly until you know exactly where the traps coming from. Then zap it until it's a puddle. Then send the earth elemental by it repeatedly to make sure it's dead.
4) Anything that needs to be poked, prodded, unlocked, or otherwise handled is done by a Summoned elemental. If it dies, you replace the next round and have it do things differently.
5) If a door is in your way, call a halt, cast Spectral Hand, and then cast Invisibility on the door (seriously - it affects objects) so that you know what's on the other side. If you decide you want to be on the other side of the door, don't open the door. Zap the door until it dies. But always, always, always see what's on the other side first.

Otherwise, just play as a normal Wizard//Factorum, spending your feats on whatever is appropriate - Font of Inspiration is actually pretty good for it, due to that ability to get quite a few extra actions in a round in an encounter.