You need a vise with wood blocks grooved for the barrel, and resin to keep the barrel from slipping when you turn the frame. A Ruger frame is pretty strong, so a wood peice about the proportions of a hammer handle placed through the cylinder window can be used to turn the frame and unscrew it from the barrel.
The new barrel can be screwed in to the shoulder hand tight, then you must calculate how much material to turn off the shoulder on a lathe to get the barrel to be sights-up when torqued into place. Also to be adjusted will be the length of the barrel extension to set the cylinder gap, and probably a touch with a forcing cone cutter, which kit (from Brownells) should also include the face cutter to set the cylinder gap. This kit costs enough to ask how much you need it, as opposed to letting a gunsmith do it.
Suggest very strongly to get Jerry Kuhnhausen's book "The Ruger Single Action Revolvers", published by Heritage Gun Books, which will describe the process, tools, and proper hand-tight angle (30 to 45 degrees) for the barrel before final torque-in to have the front sight properly straight up with the barrel at the proper torque. You may then have to adjust the length of the ejector rod housing.
