Do I have to remove the adapter-mounting plate on the back of the motor to replace the crank seal and the cam plug?

 

Yes, I believe you do. It's a good time to replace the mounting plate if it's worn.

 

The adapter, is the cam plug so yes......well there may be a plug in the first gen but it is covered by the adapter

the only cumming that i have removed are the 2nt and 3d gen and the the 3d gen has i flat o-ring in the adapter to seal the cam bore