Transmission maintenance

[Fireman431]

2001 Velvet drives behind 7.4L MPI Mercruisers. Approximately 325 hours. Not sure what has been done to them prior. The fluid looks & smells good and the levels are correct. I was wondering what are the scheduled maintenance requirements for these trannys before I smoke one. I found out it's much easier and cheaper to maintain than repare or replace.

Any help (or links) are geatly appreciated.