Did it a couple of years ago. Get the beam from Eastern Marine and the bolts too. It wasn't fun. Mine was already busted and laying in the driveway with the boat still on it. Had to jack up the boat with a floor jack and sandbags to support the hull. If it's not busted, you could launch the boat and fix the trailer in the lot. Be sure to have nut busters, and lots of tools to get the old bolts off. Took us a whole day, but it would have been quicker without the boat still on it. Mark
If the rear beam is bad now, I'm sure other parts will need to be replace in the near future. The last 4 years before buying new trailer, I replaced the drums, complete brake assemblies, several rollers, leaf springs, axle and finally had the rear beam rust out.
That was enough, went a bought new Loadright trailer from Dave's. My only regret is that I should had bought a new trailer earlier. I've now had my new Loadright trailer for 3 years carrying my 20ft GradyWhite to the fishing grounds. This past Saturday, I replace the first part, a new set of brake disc pads.
The Loadright trailer I have uses the same brake disc pads as a 1990 Cavalier. I got the brake pads from local auto parts store for a whopping $13. Also, it only took me 1 hr to do the job.