I almost forgot to share this last bit. After all of that work to get the new trailer all finished, we had to put on a new jack. We chose a Speeco 5000 lb jack.
My buddy Double D took it one step further. He not only welded the new jack on, but he torch cut the old broken one off. So I sanded it up clean and painted it with the truck bed liner. This should keep it from rusting and serving this trailer for a long time!