No hammering on aluminum cast parts. Oil pump, distributor, big no, or expect it to break.
#1 thing I have found to help disassemble these engines without breaking bolts, etc. - Heat the entire thing to 160-190 degrees F. Easiest to do if it is still running, but a space heater and a heat gun will do it also. About 2KW of heaters did it for me.
#2 thing, Kano Aerokroil or similar penetrant.
#3 patience! Carefully turn bolts, etc. feeling if the bolt is turning, or twisting off. After years of experience, I can usually tell. Once a bolt starts to move, if it starts to get stiffer again, stop, turn the other way, then go back to loosening, until it sticks. Repeat many times.