ummm... your talking about taking a hammer to a balancer pulley.... Balance.. as is weight distributed evenly..... if u do make sure its a rubber/plastic tip mallet... Ive taken em off many times.. using a pulley puller is alot easier.
u cant mess up TDC... u can only mess up the balance of the Crank and the location of which the arrow points which can affect rocker adjustments if u choose to use the arrow as a way to determine TDC... Just do what i say so u do it right