I know that it's not the answere that you want to hear, but there is really no way to give you a good estimate because the cost is going to vary a ton from body shop to body shop, as well as different areas of the country. You really need to go and talk to some in your area to find out.
Just to give you a rough estimate to get you started, I would guess that repainting the entire car with factory black paint/clear coat will cost around $1000. I don't think that you are going to get ANY body shop to agree to just put one coat of glossy clear over the black, they probably would buff right through it when polishing the finished product.
Just so you know, all solid colors cost pretty much the same, so if you like a unique or different color you may as well re-paint the car with that isntead of the black. The only cost increase associated with a color change is the fact that they will have to paint your door jambs and stuff to match, but the increase in cost is usually pretty reasonable.
If you want some kind of fancy paint or a paint process that is more than 2 stage, like a pearl or color shift, the cost will be way more. For example, I paid around $6,000 for my "House of Kolor Kameleon" paint job because the cost of the chameleon paint was soo high, and the paint was a three step process for my body shop.
