If its shallow involving a large area of thin sheet rather than a localised depression you could try pulling the dent from the outside rather than pushing it out from the inside. If you are lucky one or more powerful rubber suckers may have enough pulling force to pop the dent back into place without any dismantling. There may also be less risk of the pushing tool causing new damage to a thin panel or you pushing the dent out too far. It may not work, but worth a try first.