The pressure pump all of a sudden keeps kicking off and on.. Don't know how to determine if it is the pressure tank or the foot valve in well

Let's check the foot valve first. Shut the pump off and watch the pressure gage. It should hold steady, If it falls to zero then you have a bad foot valve. If it is bad you don't have to pull the pump. Simply install a check valve on the suction line.
To see if the membrane is ruptured take a small tool and start to tap bat the bottom and work your way up. If the tank's OK you'll hear an clunk up over half way up and then you'll start to hear a clang, The sound will be different. If you hear the same sound all the way up. Replace the tank. Good luck and let me know what you find. Tom