Help! My riding mower will no longer move. I know enough to be dangerous and can follow some troubleshooting guides to check out the transmission. Thanks in advance

This should help a bit, I am 99.99% sure that Murray makes that mower and Scotts puts their name on it. How to service Murray hydrostatic transmission? (http://transmissionproblems.org/transmission-service/how-to-service-murray-hydrostatic-transmission)