Transmission maintenance?

Hi all. I bought a 97 ski nautique (gt40 351 with pcm 1.23 trans) that was not running. Previous owner said the boat filled with water while on a lift during a tropical storm while he was gone. Water was about 1" up motor box. After that he drove the boat and said it ran just rough. He took the motor apart then let the boat sit for 2 years.

So according to him the transmission had no issues. But it was submerged by fresh water. I pulled the motor and trans and am rebuilding the motor. When I disconnected the trans lines the fluid looked good not milky.

My question is what if any maintenance should I do on the trans while it's out? I can't find much info on this. I assume there's no filter since I can't find any info about replacing one? I thought about buying the trans seal and gasket kit and cracking it open to inspect but don't wanna do this if not necessary (plenty of other projects on this boat).

Thanks for the help for a newbie!

Thanks. Doesn't look like the valve let water in. I haven't pumped it yet, just tilted and drained some fluid. I just don't know much about these trannies.