Transfer case motor replacement

My service 4wd light came on one morning. When I turned the truck off and back on again, the light went out. I have noticed that this seems to occur about every two days. I found out that there was a service bulletin from Dodge stating that the computer may need re-flashing. I had a mechanic check the problem and he thinks that the transfer case motor needs to be replaced. He also said that the passenger side exhaust manifold gasket needs to be replaced and that I it would be better to have the dealer look at it. If he is correct with his diagnosis, what do you think would be a fair cost estimate to have the dealer repair the truck?

Thanks in advance for your assistance.