When I switched to M41 (I rebuilt the transmission before hand), it seemed a litle daunting to be seaparating the OD/trans, but it really wasn't that big a deal. The trans and long mainshaft with eccentric separated easily. I would recommend replacing the gaskets on either side of the intermediate collar, as well as the seal at the output from the OD (pulling flange), the front trans gasket and the trans cover. Just be careful when loosening the 8 nuts on studs that hold intermediate collar to OD. I once snapped one of those studs and it was a bit of a job to R&R. On an earlie D type in the 444, one of these studs had been broken, and was the source of a slow leak. Also, speedo output "O"ring.