Quick, probably dumb questions from a transmission novice

Thanks again to everyone for the helpful info. Even though I probably could have removed and replaced the seals from above, I decided to go ahead and drop the valve body. Seemed to be the better way to do it.

One last stupid question...there is a metal flange surrounding the mating surfaces of the valve body and accumulator piston that continues with a "dogleg" along the front of the housing. It looks like there would be further disassembly required to replace the flange and I'm not sure I've even found the correct replacement part yet. Does it need to be replaced or will it seal again if I reuse it? It seems to be less of a traditional gasket and possibly something that can be reused, but I don't want to put it all back together and have issues because I didn't replace it. Thanks!
There is no "gasket" between the valve body and the transmission case on a 904 or 727. There is just a steel separator plate that is part of the valve body. I think that is what you are referring to. No special process or precautions other than make sure it is clean and no big deep scratches or gouges where it sits on the case. Cleaning should NOT include any scraper, sanding, or other abrasive, just solvent and if necessary a rag or plastic bristle brush. If using a rag make sure no lint is left behind. Best to finish with a solvent and blow dry with compressed air.