There's one big glaring thing no one else has mentioned here. No matter how good a paint job, unlike a factory painted car, if you get a stone chip it will stick out. A factory paint job with it's meticulous layers of paint, when a pebble hits it, one layer chips, one layer shows through.
Personally, I'd trade or sell and buy. Are the miles on this car ridiculously low? If it's an average mileage, swap. I suggest this because a good paint job will cost you much more than a comparable swap. There are black Miatas out there. You just have to look. I don't know where you're located, but try
http://www.automotivewizard.com If there's a car your looking for color included, they'll search for it. And I suggest a CARFAX report or similar. They just sound like a way to catch big problems. Used cars only.
It is your car. If you do paint it, make sure you get several coats and a good clear coat. In other words: NOT MAACO! Good Luck.