I did my 23' trailer two years ago. I went to Six Robles (sp) in Seattle to get the axle pads and new u bolts. I just raised the entire trailer off the ground with jacks. Used my air tools to drop the nuts off. Marked and cut the brake wires. Rolled the axles out. Welded the new pads opposite the old ones (which keeps the camber right). Rolled the axles back under the trailer. Installed new u bolts. Reconnected the wires. I was done in 4 hours from start to finish. Gained near 6" in lift. Perfect for the Suburban I have. It was set for a 2WD suburban before. Maybe put $50 in parts. I had all the tools and a level driveway to do it.
If you want particulars, PM me.