I also had to go to a #4 - the #3 started bending. I only had to do one (thank God). You've got your work cut out for you.
I had a friend putting MAPP-torch heat on the barrel area where the cylinder slides in, and could barely get the stud piece to turn out. Don't heat the stud itself. It's been pretty well established that that is the wrong way to do it.
Good luck.
