Lets do this.
Go here and download the operators manual:
http://www.manualslib.com/manual/339...l#product-1610 (393)
Then, go here and get the service manual.
http://service.mtdproducts.com/Train...0/772-3870.htm
Figuring out the dump valve should be pretty easy. Why don't you get it freed up first, then see if it works in one position. If not, move the lever the other way. Little trial and error is pretty simple. It only has two positions. In one, the hydro freewheels, in the other it works. I know your young and new at this, but lets not make it harder than it is. Might be able to spin it with a drill or something.