If it were me I would remove the whole assembly. It's easier to mate
the motor up to the tranny out of the car and it would give you a
chance to clean out the engine bay more thoroughly.
My 2 cents...
-Jeremy
I would agree with Jeremy that it is easier to deal with the whole thing as
a unit. Yes, the spring pin can take some effort, but that is about it.
You will want to have ready access to the tranny outside of the vehicle to
get the adaptor plate and motor assembled, so I think it is the best
approach. That is what I did for mine, and had no issues with it.