You need to have him itemize the work. It shouldnt take him more than 20 minutes to work up a very close estimate.
I am havign my truck repainted in spaces from it being egged. Tailgate, Front hood, Passenger door are being repainted. Rest of the truck is getting buffed. He is also tapping out a few door dings, touching up some paint and replacing my tailgate Ford Emblem to line up with my Texas Flag Emblem (I have Grand Prairie Ford letters under the Ford one, but wont anymore).
Anyways, I am getting all of that for $880 (well, insurance is paying).
Hmm, now that i think about it, with the custom work you are getting, 5k might not be too bad, but I would still have him itemize before agreeing to a price.