www.championtrailers.com
look in the tech article section, all you need to know about adding brakes...
Not a hard job, the part that took the longest for me was snaking the brake line through the frame. I added a pair of 10" surge drums a nd it made a huge difference in towing my boat. I check the brakes every 4 seasons or so, I started lubing the piston in the wheel cylinder with OMC triple guard grease and I found that it keeps the piston from seizing up and if you do that and grease the threads on the brake adjuster it keeps them working well much longer....
A few years ago my brakes locked up on our vacation. I was able to order a complete brake kit from these people they also sell kits to install on a trailer which does not have brakes. I was always under the impression that disc brakes were better for boat trailers then drum. That is probably another topic well discussed elsewhere on this forum.
My trailer didn't come with brakes and I was able to add electric brakes (drum, not disk) with parts ordered from an outfit on Ebay. A pretty easy modification for anyone with moderate DIY skills, and they have worked great. You can find them on Ebay at http://stores.ebay.com/R-and-P-Carriages-Trailer-Sales; just look for brake kits.
I've pulled trailers with surge brakes and electric brakes and I prefer the electric brakes. I don't know how much more it would cost to go electric but you might want to look into those. My truck had the factory tow package and was already pre-wired for a controller so it was really easy to hook up. If your tow vehicle isn't pre-wired it would be a bit more work to add a controller though.
My trailer didn't have the flanges for brakes, so I replaced both axles with new axles including electric brakes. 2 each 3,500 pound rated axles with brakes delivered from Lubbock, TX to Black hawk, CO for about $950. By the time I added the rest of the electrical stuff, and got it all together it was about $1,150.