Sorry to hear of your problems.
There is very little difference between the MS2A-D and MS2A-E....the "E" was the follow-on model to the D. The difference was that the E model had shot peened gear
wheels for a bit more strength, and the E used heavy gear oil
instead of engine
I cant see any reason that the gear cannot be removed from the boat with the boat still in the water
unless there is something that would preclude sliding the shaft back a little. Just shut the cooling
water thru hull
valve, disconnect the hoses, cable and mounting bolts and pull it out.
is it mounted to? There shouldnt be any problem interchanging the models if they are the same reduction ratio.
I have a new-in-the-box MS2A-D gear in the 2.40:1 ratio if you are interested in a new unit. (There were two ratios available, 2.04:1 and 3.00:1)