The survivor stock setup could easily be sold to offset the cost of a new stock set, and anything is more comfortable than the plastic stock butt plate. That said, I'd be interested in the survivor stock, and might even trade you for a decent wood set.
Try the 308 with a better butt pad before giving up on it as a full powered rifle. If it's still too punishing find a good cast bullet and have fun with reduced loads!
Others have addressed it, but if the lockup is solid there isn't an issue swapping barrels. Saying it needs to be done by h&r is like saying only your car dealership can change the brake pads on your car. It takes some intelligence and knowledge to fit a barrel, but it ain't rocket science.