Your correct, you an use an isolator to allow bonding of the two types of paints. It is a highly flexible paint that actually etches and adheres to the underlying paint. They can successfully be used to paint over acrylic and incompatible paints. I would be more concerned about the quality of paint being used in the elcheapo paint job.
If you are doing all the prep work yourself, laying the paint is the easy part. Why not ask for some advice on how to prep it properly, and get it ready for paint.
If it is ready to shoot, you won't pay much for a decent job. They won't accept responsibility for the work because the finish is all in the prep, but you have a better chance of a good finish for your budget.
Alternatively ask someone on here to show you how to paint yourself. Your car sounds like the perfect thing to cut your teeth on and pop your spray gun cherry. I'm not a painter but asked a lot of questions, took my time and over the years the finish is better and better. My cars have gone on to win multiple concourse events including RACQ restored car of the year, and even received an award for best standard paint on my sisters mini, which was painted outside on the driveway under a tarp. Its a skill that will save you thousands and is very rewarding.
If you want any guidance, I'm not near you but PM me and I will assist where I can.
Greg
