450SL reverse band servo piston removal,how?

Does anyone know where to get the seal or piston parts for this? Next, how hard is it to replace myself if I can't find a tech to do the job and how do I do it? Is there a way to verify it's the seal without the air pressure technique by removing the piston? I'm a little scared of local mechanics messing with it. Also the modulator setting, when we first installed the XMSN it shifted a bit hard. I adjusted the modulator clockwise 3/4 turn.

thanks again,
jmdunn

[mbdoc]

The cover has to be depressed & then snap-ring will come out. Most trans work is best left to "pros".
Turning the modulator clockwise will stiffen the shift even more!