My attempts to rearrange the dungeon so that the PCs would find a potential ally before the final confrontation were for nought--the PCs decided to save their fighting capacity for important fights.
Limit-testing #1: the players missed Theodocious' hint that "the golem's vulnerability is in the left arm." They did detect magic to find the two bolts of shattering hidden in his forearm, but they fixated on the golem's arm as the weakness, and didn't make the connection that those would be particularly useful against the golem. I was surprisied that they didn't figure out this riddle, since they had just used a detect secret doors to learn that when Theodocious said, "you can find the information I have in the chest", he meant his own chest, not the wooden box on the floor. This was the first time I can remember the players missing a riddle
Limit-testing #2: The PCs went on into a garbage room with self-organizing constructs that could only be put down by mass attacks. They were no match for the PCs, really, except that the PCs were trying to save fireballs. So the PCs ended up knocking them down into disorganization and running past them before they could reform. Which was a neat result.
They also showed wisdom by detouring around the door that was locked from this side. More for their mop-up the next day.
So then they entered a large room with two doors; behind one door was a flesh golem, behind the other was a stone golem. They picked the flesh golem first. Its 15/+1 DR availed it nought against them--all the attackers had +1 weapons. (I am really hoping that D&D 3.5 does a better job with DR. As it is, DR X/+1 is basically irrelevant against my party.)
So after that, the stone golem came out. (The module said he'd wait five rounds, but the flesh golem was dead in one or two.) The golem's left arm was sheathed in steel plates--it had also read and misinterpreted Theodocious' words. The golem turned out to be a really heavy hitter--not terribly mobile, but +18 on each of two 2d10+9 attacks, and 15/+2 DR. (I reduced the DR from 30/+2 to 15/+2, because I wanted Turok's heavy attack to have a chance of doing some good.)
Various out-of-order bits about that fight:
Their most potent fighter turned out to be Slade (Liandra's awakened dire wolf companion) with greater magic fang, since he could actually harm the golem. Unfortunately, his AC was low enough that the stone golem was almost certain to hit him every time. Slade has more hit points than anyone else in the party, but still ended up visiting the unconscious zone.
Prolix tried to sneak by the golem invisibly, but did get heard and battered once. In the big room beyond the golem (which had been the sanctuary of an evil temple in the module as written), I had put two things: a dragon-shaped construct in progress, and a large piece of clockwork with which the metagolem was destructively reading Theodocious' papers. (The module had provided no explanation of what happened to all of Theodocious's spellbooks and journals. I rationalized away their loss with this contraption, more or less conceived as a scanner with razor blades instead of lenses.) The reading machine served as an unintended distraction to Prolix: he cast a detect magic that informed him there was some magic in the area (the spellbooks and scrolls), and fired one of the bolts of shattering into the contraption. Which destroyed it very impressively, but did not destroy the golem. Had I not put in that extra scenery, Prolix might have gone on to find the actual metagolem.
Kyle's dagger was greater magic weapon'ed up to +2, so it could hurt the golem, but not do a lot of damage.
Liandra managed to score a critical hit with her use of rusting grasp against the golem's armored left arm. I described all the armor-plating falling away--sadly, there wasn't a particularly vulnerable spot underneath. I gave attacks against that arm a +2 to damage, though.
After a bit, the fight got pretty tense--Slade, Turok, and Kyle were in melee around the golem, and all of them were fairly badly damaged. I didn't fudge any rolls in this combat, but I did start fudging tactics: I let the golem fall for Turok's ploy of trying to draw attacks of opportunity so that Slade could withdraw, and I let the golem choose to pound on the healthiest effective assailant, even when that meant not finishing off someone.
One particularly scary moment: with one attack against Slade, the stone golem rolled a 20--and Slade's armor class was so low that the golem would confirm a critical hit unless he rolled a 1. A critical hit would do at least 20 hp of damage, enough to kill Slade... but I rolled a 1 to confirm the critical. Woo!
So this was the third bit of limit-testing; the battle left them all alive, but feeling very drained--a very good result. I could not ask for a better result from the combat. My only regret is that the players were aware of my merciful tactics. Oh well; they already know that I'm trying not to kill the PCs.
I was trying to have the metagolem talk to them during the combat in an evil-mastermind now-I-will-reveal-my-plan-and-clear-up-a