It will be expensive for a body shop to do this. A good body shop usually starts at 80-100 bucks per hr for labor. You would have to paint everything not just the spots.

I have seen some diy jobs like this around here and they only look good for a couple of months then everything started coming apart because of chassis flex and road wear. They had used a urethane filler and then a body filler over it and it looked like crap.

If you try it use a flex agent in the paint it may help reduce the spiderwebbing between the urethane and sheet metal panels.