Well, as I said, I don't think I'll get more than $50 for a virgin blue VM in unknown operating condition... so I probably wouldn't even both selling it.
But I think I should concentrate on getting a proper functioning gun to bring to the field first and then fiddle with my VM in the meantime.
Even if I wanted to swap my valve spring, what would I use and where would I get it?
VM-68: Heavy is good, heavy is reliable. If it does not work you can always hit him with it.