Depends. Some new, old stock barrels are short chambered and will need to be finish reamed. Used barrels will usually be OK. There was a long discussion on this forum recently on Carbine headspace. The consensus was if the bolt closes on a sized case and it will fire, you are good to go. Since the round headspaces on the case mouth extreme excess headspace would lead to light primer strikes but anything tighter than that is OK for the moderate pressure, straight cased cartridge. Not ideal, but safe.
The front sight can be transferred to the replacement barrel.