Rebarrelling with a commercial barrel won't help its collector value. Is the barrel that is on it now '43 SA? If so, that could be the original barrel, and some collectors like that, even if the bore is not good. Has the rifle been rebuilt over the years? Have you tried thoroughly cleaning the barrel? Perhaps you should, and then shoot it, and then clean it again. It might not be as bad as it appears. If the rifle has been rebuilt over the years, installing a GI barrel dated '43 or later shouldn't affect collector value, apart from having a better bore. But you may not recover the cost of the replacement barrel - and there could be headspace and indexing issues if a used barrel is installed.
Changing a barrel requires a barrel vise and an action wrench, as well as headspace gauges, and a way of insuring correct index.