Yes, sun valley is the best if you are removing the tranny your self, but all the work is in removing and installing a transmission. Fixing the tranny(one of these .3 ) is the easy step. Fixing reverse is a weekend job...This transmission is well documented on the web on how to fix. I guess by your email you are hurting(alot) to pay the 2k

Experiment on your old one. The reverse is fixed this way. It is the small rubber lip seal

722.5 transmission oil pump rebuid DIY - Mercedes-Benz Forum

Experiment on your old transmission.

Martin