WHAT CAN QUITE OFTEN HAPPEN IS THE MECHANICAL PARTS OF THE LOCK IN THE DOOR CAN GET TIGHT & THE MOTOR IS NOT STRONG ENOUGH TO PUSH IT, YOU CAN USUALLY TAKE IT OUT & FREE OFF WITH WD40 THEN REFIT, NO NEW PARTS NECCESSARY, THE THING ABOUT THE ALARM GOING OFF & BEING ABLE TO TURN IT OFF ON THE IGNITION WITH THE KEY IS A STANDARD VAUXHALL THING.
you can fit a modified breather box in the crankcase system, then clean out all brass fittings to the throttle body & clean throttle butterfly & idle control valve, this should sort it.