I change mine every season and have never heard anything like what you
are relating. There's no "seal" that I'm aware of and you don't change
the reservoir unless you are changing the type of lubricant, for
instance changing to synthetic. You should also be checking the lube
fowater, the gimbal bearings, bellows, U-joints and lubricating all
those things that need lubricating. I don't do this, by the way. My
mechanic does; I just speak the language!

Capt. Jeff