Earlier posters mentioned a barrel vise-this is only one part and can be 2 pieces of wood with a v channel in it to clamp the barrel in a good vise.
The really important part is a frame wrench. This item supports the frame while removing the barrel of double action revolvers. Brownells lists their own complete frame wrench for K frames for $140. Which, while expensive, is way cheaper than a new frame. Different heads, to allow the wrench to fit other frame sizes run about $100 each.
Trying to whittle one yourself without knowing what part of the frame you have to use as your leverage point so that the frame won't get warped isn't worth your time.
Replacement barrels don't just screw in. The "draw"-the amount the barrel has to turn from finger tight*-may have to be adjusted, as will the barrel/cylinder gap and possibly the forcing cone.
*Yes, you can force this. The result can be a cracked frame tenon where the barrel screws in.