Can't help you with the owners manual but you might try E-bay. Also the Clymer's workshop manual would be usefull if you intent to do your own maintenance.
Regarding the fuelc0ck:
Handle forward= reserve, down = normal run position
PRI = prime.
The first 2 require vacuum from the carburator and is only supplying fuel when the engine is running.
PRI = unrestrited flow of fuel.
Fuel capacity is 10.5 liters of which 8.5 liters is available for normal running ( approx 100 miles or 160 Km to be on the safe side.
Ther's NO gas gauge but you have a look through previous posts and find the solutions other members come up with.
Also read the instructions for posting on top of the list.
Greetz
Kropatchek