sh*t man, you don't need but 200$ for a flat black paint job. It's almost impossible to screw up that. If you don't have experience just paint the inside of the trunk first to get a feel. You can touch up without feathering, overlap, etc etc and you won't notice the difference. The good thing about it is you don't need to work the paint after its sprayed, which saves big bucks & a lot of time.
A good primer will be around the same money, but this depends on what primer you use.
If you want it to last a year or more (with a car cover, any primer will get beaten open to the rain for more than 2 years) just use a 2 stage with a quality filler primer. Touch it up within that time when you're ready for the real paint.
Just read you won't be keeping it outside...go with the 2 stage primer, it's the best choice unless you plan on keeping it that color for the rest of your car's life - then go with flat black.