Well you can try to have it replaced but this type of shaft doesn't often take well to this type of repair. The RIGHT way is to have it sent out to be rebuilt AND balanced. Driveshaft balance is quite important and some shops aren't too careful about this, or able to deal with it once they've removed the shaft and banged on it. Also the trueness of the shaft has to be measured to make sure it isn't bent. I presume the center support bearing/mount has also been inspected?
I guess this is the shop's call---if they've done it before successfully, then maybe it's worth a shot. If they are saying "no guarantees" then maybe you'd best go the other route.