So far, the guesses have been pretty right-on:
1) Yep, it's modular, but I think our adoption of modular games dates back before BrickQuest. BrickQuest came out in summer of 2003 (or thereabouts), and our first BrikWars module game was on Jul. 15th 2002.
2) We didn't realize beforehand that someone who shall remain nameless (ELROY!) built a module that didn't quite line up with the standard, with a door in the middle of a 32x32 rather than in the center of a 16x16. But we used the module anyway, and just pretended that everything lined up. It didn't end up affecting the game negatively, so we were all good.
3) We've got a bit of text on the NELUG site, but not really a bona fide writeup of the game summary.
As for the rules, we sort of arbitrarily set out a module standard and had everyone build as many modules as they could before the game. Everyone showed up with between 1 and maybe 12 modules (I had 4), and we had about 20-30 modules between 7 of us.
We started in two of the larger rooms (one team in one module, one team in another) but nobody knew at the time how the modules would connect. The only modules on the board at the time were the starting modules. Then, every time someone would try and open a doorway, we would roll a die to see which module got attached to the newly opened doorway. Gradually (and obviously very randomly), the board unfolded.
As for other games we've had, I've got some comprehensive lists of stats and such on my site: