Changing the race, baseclass and class files is similar to the config file, but easier.
I haven't seen Steve McDonald around in a couple of months - he's usually on the Yahoo list anyways - but he had done quite a bit of work with these files for his Dragonlance project. I've just played around with naming conventions and seeing how DC handles stuff compared to what the code says.
I'm pretty sure if DC ever gets away from MFCs, I'll be able to help a little more in the coding department than I have in the past. Unfortunately, I've not been able to figure out any of the bugs, but I have gotten some pretty good ideas about a couple of feature requests. What I have no clue about coding are the special abilities. If I could figure those out even a little bit, I'd go to the trouble of tracking down the software I need and installing it just so I could get those done, well more correctly, help get those done (hopefully help get those done).