Speakers in the dash are very easy to remove and as far as upgrades a lot of people like crutchfield. The pods on the roll bar come off very easy with a torx bit, from there remove the cover on the speakers and you should be able to see how to disassemble. (may need to have top off or at least folded back to see what you are doing)
For me I changed everything from stock and probably paid too much but ordered all my speakers and head unit from quadratec, I think it made installation easier. I now have 16 speakers that I can hear on the highway with top down (haven't tried yet but I am sure) I didn't do it all at once though a little at a time. I did replace pods with a sound bar. This moved the speakers directly overhead-I think that helps a lot.