Small Engines (Lawn Mowers, etc.): john deere 125 auto

Question
I bought a used deere 125 auto lawn tractor it started leaking something out of the rear 1/2 of the mower and now it will start but will not go either forward or reverse  help

Answer
Was the fluid an oil or gas fluid?

Based on where the leak is it sound like it might be transmission fluid.  You will need to use a flashlight, and maybe raise the mower, to see where the fluid is coming from.

Is the engine oil correct?

Did you check the User's Manual?
http://manuals.deere.com/cceomview/OMGX21821_H5/Output/
Eric