I put 6.5" speakers in my bar too, which is quite a jump from the original 4 or 4.5, whatever they are. I had to drill new screw holes, but i didn't even have to get the fabric out of the way, just drilled right through it.
The speakers you buy should come with new connectors to splice into the existing wiring, but it's really not hard to do as long as you have cutters and a crimper.
The drilling was also easy, just get the right size bit for the screws. It looks completely professional and there's no technical problems with the bigger speakers