I assume you are trying to get the old tumblers out so you can just replace them in the old lock. the hard part is they need the old key to enable you to turn the lock set to get the tumbles cylinder out. I would suggest carefully dissassembling the old one, with a drill if required, but look closely at the new set so you don't damage anything other than the old tumbler cylinder. pry the cover off and then work your way in or whatever it takes. once it is out then the new set simply slips in. there is a small hole in the face, next to the key hole, where a pin (paperclip) can be inserted and, if you had the old key, that is where you would turn the key to on, insert the pin (paperclip) and then turn the key backwards all the way,with a slight tug outwards, until the tumbler cylinder comes free. if you could drill out the tumblers without damaging the lock you could still do that. just be carefull that the drill doesn't grab and suck the bit in too far, damaging the switch. worst case scenario the new switch won't break the bank.below is a youtube that shows how to do it
https://www.youtube.com/watch?v=BqMwQ-yfLWs