Come on, Rob, don't make me second guess myself here!
It's not that hard really and the 904 has to be one of the simpler automatics you will ever run across. There are only a few parts to deal with, it's really straightforward. Only a few special tools required if any.
I guess things like getting the servos out and back in, dealing with snap rings and checking clutch pack clearances are a little involved but no more so than building a performance engine. Doing it all while the thing is out of the car makes it much easier as well.