Axle dolly made replacement pretty easy.
I changed my axle by myself today & was pretty concerned about getting the new axle under the trailer before jacking it into place. I had a 2x12 lying around and attached some casters to it. I used this to remove the old axle and then to put the new axle into place. Other than having to go from one side to the other on the trailer more than I would have liked, this really made the job pretty easy. Maybe there are hundreds of other posts using this technique, but it sure made this job easier than I expected.
I think I'm getting close. Maybe, after 2 years of work, I'll be ready to take the trailer on the road this spring.