I only go by references for an expense as this...something long term and cost over $4k. I would want to see work being done, know what they will use for primer, base and clear, know how many base and clear coats. Best to see a paintjob on someone elses car and ask.

If I plan on keeping the car for over 10 years and its a low production or numbers matching, I would spend more money for a higher quality paint and painter.

You can save a lot of money in labor by removing your interior, glass, trim, bumper and taillights yourself. If you remove the glass front and rear, the paint will look better and its a marginal reinstallation cost.