DonT,
John's given you some excellent advice. The question you need to ask yourself is, do you want to pay what you could build one for, or get a bargain?
$800 is a fair price, but you might be able to put one together for that price, or less.
My last Rolling Block project went this way.
Purchased an action for $150, Green Mountain barrel for $125, some nice deluxe wood, for $100 (fitted it myself), sights for $150 front and rear, bluing for $160, fitting barrel to the action $140. Total-$825
The project before that started life as a barreled action, that someone didn't want to finish. Bought it for $300, and for another $300 I was done!
It's generally tough to get out of a gun what you put into it, unless the project is a correct restoration of a mostly original gun.