cuccman

I recently purchased a used Craftsman 12.5hp lawn tractor with a hyrdostatic transmission. After thoroughly checking the tractor out, I discovered that the cooling fan was broken, and the transmission fluid was low. I ordered a replacement cooling fan, but since I do not have the manual yet (also on order), I need to know what type of transmission fluid is used, and if there is a way to drain the old fluid from the transmission. The fluid looks very dark (almost black), probably because the cooling fan was broken for who know how long. I have been told by a Sears "specialist' that the transmission is a sealed unit, but I want to believe that there is a way to get the old fluid out. Thanks for any help.