If it is still running. why do you think the head is warped. Is coolant leaking to the outside, is engine oil getting milky. If so you probably warped the head. If the oil looks good and no external leaks you are probably OK. If you do need to remove the head. Get a good manual (Haynes if possible Chilton's is OK) follow it to the letter and you will be ok. to depressurize the fuel system disconnect the fuel pump electrical at the tank and run the egine until it runs out of fuel.