As far as links go here are a few that I order from that are really good. Good prices and really fast shipping.
www.autogeek.net www.detailcity.com (also check out their forum for any tips)
www.premiumautocare.com www.bigwhitemarine.com I just ordered a dual action polisher from Autogeek with all the different types of pads. It is the non Porter Cable one, but it is just like it, but a little nicer version, more adjustability and counter weight already attached. It is also on sale this month
. On their site it has a great tutorial on which pad to use for which application and you can order accordingly. A dual action is a lot better because you run a smaller risk of messing up the gelcoat by burning it. If you have experience with the Dewalt then go for it (that is actually what I had first before the DA polisher), but I just wanted something that I knew was extremely safe for my boat.
Also check the search for Grant's writeup on How to buff gelcoat. He did a great job of explaining and he even took pictures. Good luck!