Good news is I'm 6'2" and have long arms.......and need them to reach the mast insert area. There is room to work but in trying to get the mast tube out the other night .....whew it was tough.
To ensure a proper repair having good access is essential. If it was me I'd be putting an inspection hatch on the bulkhead forward of the rear drive. I added two 4" hatches there on our old Oasis, as well as a few more and had no leakage or other problems at all. The pics are gone (and I have long sold the Oasis) but there is some info in this post:viewtopic.php?f=11&t=12042&p=73826