I've painted many cars & I can tell you that if you are getting the liner first... . you will have problems with paint peeling along the seem where the liner meets the paint. This is because the painter won't be able to sand against the liner really well & also it will be a butt edge. This is what you don't want [butt edges]. Water, snow & dirt over time will make the paint peel. Also make sure that the painter takes your door handles & trim off or the butt edges will peel. I say paint first & wait 30 days for the paint to fully cure... then the liner. Just my advice.