depending on what type of paint you go with probably anywhere from $250-600. Depends alot on what they have to do, what kind of paint your going to get and the shop you go to. Not sure in your area, but those prices are about right here.
I paint cars at home in my leisure time and I would do the engine bay and interior for about that amount. It would just depend on how intricate the work needed to be. I know guys that pay better than $3500.00 to have their Harley tanks and fenders shot with a simple custom job.
Check out a Maaco if there are any around you. Explain to them what you have and ask them if they can do it if you supply your own materials. A lot of them will agree to do it but there would be no warranty. That way you would have it sprayed in a booth and dustfree.