I almost did this conversion a few months back, but as I previously posted ... went with the 7000# drum brake assys as they are noticeably better than my old 6000# brakes and satisfied my needs on my 3150RL. $1500 - $1800 seems to be the ball park price for a do it your selfer. Here's a pretty good video of one guys swap on a trailer similar in size to ours.
ETrailer and Eastern Marine have good prices on most of the parts. EM has a better price on the controller if you go with the Titan BrakeRite brand. I think running the brake lines is the hardest part, but not impossible. I like the idea of running the width wise brake line run once across the frame instead of on the back of the axles like some videos suggest. The swapping of backing plates for caliper mounts is a straight forward and rather simple task ... as in the video, you may need longer bolts however. If you do have to double flair a line ... it's no harder than a single flair, just one more step with the right tool.