Yeah the self tapper method works. One time i had just put my engine back in and got everything connected up bar the selector rod. I then realised i handt fitted the boot kit and new seal that i had bought. I managed to get the old seals out with a drill and self tapper with the car on stands. Just make sure you dont damage the internal bore otherwise it will never seal! Also remember if you still have oil in the sump, oil will spill out when you take the seal/seals out. Wait until your next oil change i suggest or do an early oil change