Yeah that sounds like WAY too much!! When he says differential I am sure it is something in the third member only. You can buy open, used thirds for as low as 80 bucks. Of course they have to match your gearing, but they are out there and it is super easy to replace yourself. As far as shocks you can get some good ones like Fox or I saw some SAWs recently for 300 bucks and you can rebuild those if they ever go bad. Replacing the rears is a breeze, but the fronts are a pain in the arse. Don't let this guy steal your money, time to upgrade!!!