leaking badly & not cleaning dishes

You need a properly sized hex (Allen) wrench to get the screws out. Basically simple: remover bottom roller tray, unscrew large plastic holding bolt, remove lower spray arm, unscrew bolts (be sure the wrench is sized right or you might strip the heads), and replace gasket; then reverse procedure. Chances are if the gasket was bad, it will be very obvious (out of circular slot and stretched).