I lost the right Hydro unit on my MZ Magnum and tried replacing gear oil and checking all points that BB service suggested. I purchased a new sealed unit but can find no info on replacing. Any tips? If not I will figure it out, just hoping to learn of any pitfalls. BTW The unit has 280 hours and was told it is rare that one of these hydros go out this soon. Mowing 5 acres no hills