Tim,
After enthusiastically accepting Jimbo's offer to provide me with "developer access", I quickly soured on having any hands-on participation.
It was as I feared: no requirements documents, nothing about architecture or detailed design. The hardest-working, most universally respected developer(s) kept basically saying "just read the code".
So I've kept on the sidelines. I've been a cheerleader and catalyst (for speed tweaks) and for many months a sort of chief sysop (carrying out bans and promotions).
As for your request for suggestions, I think the best thing would be to adopt some sort of "best practices" methodology. I don't care if it's XP, CMM, or just a checklist of common- sence guidelines from Steve McConnell's "Rapid Development". Adopt some mutually agreeable (and useful!) guiding principles, and follow them: that's what I suggest.
Ed Poor Highly Paid Professional Software Engineer