Larry, if it is a collector grade gun, meaning in very high original condition, then I agree with Mike Harrell. However, if it is well worn but solid then I'm going to say opening the chokes won't really lower the guns value. Especially if the choke work is done by a top gunsmith. I've asked the same question of several major dealers and this is basically the same answer they've given me.

When an old man dies a library burns to the ground. (Old African proverb)