To answer both questions, yes.
There is no such thing as a "press-fit" barrel in a S&W revolver, or "crush-fit" for that matter. S&W barrels are fit just like barrels in any other firearm, rifle or revolver of other makes. They are threaded and screwed into the frame with a degree of "Draw", the force needed to fully seat the barrel once the shoulder contacts the frame. The difference is the later non-pinned guns use a little more draw (torque) than the pinned guns.
The pin never did retain the barrel. It was merely a safety device so that if the barrel did loosen in the frame it was limited in how far it could turn. This was so, even a gun the barrel had loosened in, would retain barrel alignment so the gun would continue to be functional, even if accuracy were affected. This could be very important to a LEO in a bad situation. With the increased torque values there is less chance this could happen so the pin was deleted as a cost-cutting measure.
New barrels, for the same frame size, have the same thread diameter and pitch as older ones, so a new barrel can be used in an old gun. In either case, a used barrel being fit to a different frame may need to be set back a turn to obtain proper draw. If you are going to re-install the barrel pin a groove for it will have to be filed across the barrel shank.
Unless you remove the barrel to replace it, or set it back a thread to allow adjustment of the barrel-cylinder gap, why would you comtemplate removing it at all?
