Welcome to the site.

1. What George said.

2. With a blown barrel, the gun you have has value only for parts or if you can find another set. In other words, next to no value. So, don't think you'll be destroying its value if you get a new barrel sleeved to it.
That said, the comments upthread reminding us of the extreme cost of sleeving - if and when (a) there is a craftsman to do it and (b) it can be done - are useful. They also point out that, if you should be able to get it done, you're almost certain to be underwater on the gun if and when you come around to selling it.

fiery, dependable, occasionally transcendent