Go for it, it's not hard to do if you have some basic mechanical skills. I changed mine out a couple of years ago and went with the tie down stainless disks. They are not very good in my opinion. The wore out really fast and ran really hot.
I replaced them with Kodiak's last spring and they are much better brakes. I would pay the few extra bucks and go with Kodiak's for sure. The Kodiak's also have a gear oil hub instead of a grease-able hub, might be why they run cooler? Tie down does make a ventilated disk now which is probably way better than the unventilated disks I used first. Also, I would never go back to drum brakes on a boat trailer.
One tool I found helpful since I was working alone was a vacuum pump for bleeding the brakes without having to operate the actuator.
I reused my master cylinder but replaced all of the lines with stainless steel units. I read recently about a flexible hose kit for boat trailers that sounds like a good system. I don't remember who made it but it was around 100 bucks for a single axel trailer. That's about what I paid for ss lines.
Go for it, you won't be sorry
