The dip stick by your right foot is the ONLY one for the trans/differential. If it reads full on level ground ur good to go :-)
The inspection plate under the tractor is for access to PTO clutch adjustment. There is a bent cotter pin hanging from a hole in her belly, that is to keep the hole open for any seal leakage.
I drilled an extra hole in the center of the inspection cover, installed another cotter pin in it also. Then if you have an oil leak, front hole=engine, rear hole=transmission.