Back left corner of the fighting compartment. It's precise position is dependent on the model of Sherman as M4A3 and M4A4 have the air cleaners close by which alters it's position very slightly.
It has electric start by exciting the windings, provided that there is some power in the vehicle batteries or you can rope start it if needed.
No cover, not particularly noisy but you weren't supposed to stay in the tank when it was running in case of exhaust leaks. Radial engine tanks duct the cooling air into the engine bay or fighting compartment to act as a heater. On other models, it just blows wherever!