i just went thru haulout exercise, worried about water same as you, and mechanic
checked oil. No sign of water so no seals change needed.
I also get varying level on dipstick. If you get that and you worried, undo nut on the top of saildrive
where is says oil and air pressure will equalize immediately and you should get correct reading.
Oil ... maybe you spilled it and now can't clean it properly ?
there is lots of negativity about SD 50 on internet
, probably couple of disgrunted customers raising noise
, so you need to do your own checking.
My saildrives are after cone service
in great condition after 500 hrs.