OP, if you want to spend that much money on a new compressor, then go ahead. I did my paint job with a 26 gallon, 4CFM@90 PSI tank and it sprayed fine. I don't know off the top of my head what the CFM requirements on my gun are, but I had no problems. Unless you wan't that big of a compressor anyway, because you have other tools you would like to use, then go for it. But to spend that much money strictly for the spray gun, IMO it's not worth it.
I let the paint cure for 24 hours in side the garage. Maybe it wasn't long enough
, but I had to work in the mornings so I didn't have many options. It got rained on a couple times, but no more then 4 or 5 days after I had sprayed. It was nasty, dirty rain and I let it sit for quite a while like that because I didn't have the top on and didn't feel like washing it. And I used a single stage, so maybe not having a clearcoat makes the paint more prone to water marks. Anyway, it's nothing a good polish can't fix. I polished and waxed a door last weekend to see how it looked and it looked damn good.
Good point on letting the paint breath, I forgot about that. But that's why I haven't waxed the rest of the Jeep yet, I just spaced on that point.