Is it tricky getting paint to stick to urethane? If so, would I be better off buying a rear deck lip spoiler that is pre-painted by a co that does hundreds of them vs a local paint and body shop or should they be accustomed to urethane also?

 

a local shop should be able to do the job, its not any different, just the primer is different, the paint would most likely match better at a local shop because they can see the actual car and match it to that instead of a generalization. But you decide. less hastle vs more exact