Monty
First of all, welcome to the forum.
The barrel is not hard to change out but you do have to use a bit of caution. You are in good shape if you have a vice. Obviously a wood vice is best but a metal vice will do IF YOU USE SOME WOOD LINER BLOCKS. I guess you don't really care about scarring up the old barrel but putting in the new barrel takes some care.
The barrel is a standard right hand thread. Take the cylinder out of the pistol. Clamp the barrel in the vice. Don't clamp it too tight. Just tight enough to keep the barrel from shifting in the vice.
Hold the frame with your hands. You should not need a tool. You should hold the frame as close to the barrel as possible. That way you will be putting all of the twisting force on the strongest part of the frame. I have heard or read of folks inserting a turning stick into the cylinder opening as a way to get a mechanical advantage if the frame won't turn on the barrel. I don't recommend that on a brass frame pistol because of the danger of breaking or deforming the frame.
I have done this on a lot of pistols both brass and steel and have never needed anything but my bare hands and never needed any penetrating oil. It works on the 1863s as well.
When you put the barrel back into the pistol, you will want to carefully watch sight alignment. Stop turning before the sight reaches line-up and then carefully and slowly turn it until the front sight is in perfect alignment with the rear sight groove on the frame. I always did this by eye looking at the sight alignment as I hold the pistol as if to shoot and also by examining the flats on both sides of the pistol comparing the line-up with the flats on the side of the frame. The barrel will tighten up somewhat before the sight reaches perfect alignment. Maybe twenty or thirty degrees. You can keep turning until you get it lined up even though it will give you a little resistance to turning.
I have some ABS plastic sheet from which I made some vice liner blocks that I use for this purpose. I will be happy to send a set to you if you give me your address.
I will trade them for a Signature Series Second Model Dragoon with box and papers, unfired and unturned with the flask, mold, and nipple wrench.
Okay. Okay. No charge. Seriously, just give me your address and I will send them out if you need them.