If the 5k offer was real, I'd seriously consider it. That's about as high as I have seen people get for it. Yours might bring more at a good auction, but there you have to deal with fees etc. Even if he doubles his money on it, there's no guarantee you will without his connections, people to plunk down 10k don't grow on trees.
I used to love being able to hit hard at 1000 yards. As I get older I find hitting a mini ram at 200 yards with the 22 oddly more satisfying.