close to lpg tank(s) there should be a valve, close it off and that seals the tank off. there should also be solenoid valves, these are located at the tank and at the inlet to the vapouriser, you can pull the wires off (put a bit of tape over wires to avoid shorts) this will also cut the gas off. there is no chance of gas escaping and it should not unless the valves are faulty. with out power the solenoids are closed!
you dont need vin for parts, most good suppliers can get parts just from reg. if its for eka code the number you need is in the window, under where you put tax disc, just riveted to dash area!