Revell made a 1/48 B-17F, Monogram has been a steady supplier of the B-17G in 1/48, kit 5600. In 1/72 Academy has done almost all of the earlier B-17's, and Hasegawa has also done the G at least in 1/72. Revell has also done one in 1/72, but it is a very old kit, not nearly as nice as the others that are newer.
You may want to start with a simpler project, the 4 motor bird can be complicated. The 1/48 Tamiya F4F-4 is recognized as being very easy to put together, the parts fit very well and it is a very good replica using just the parts that come in the box. The Tamiya P-47 kits are also well regarded in 1/48, and since you like WW II subjects might be to your liking.
Painting any kit is the steepest part of the learning curve, with filling and sanding to get rid of the seams being the next hardest part for me to get right.
As to the air compressor, the least expensive route is one of those made to pump up tires and available at K-Mart and so on. As I remember they are battery powered or plug into a cigarette lighter (12 volt, use a small Gell Cel battery or motorcycle battery). I use a 2HP shop compressor with a storage tank built, way overkill as an airbrush needs only 10-20 psi and not much volume. The nicest are the ones made for airbrush work but they are expensive. Most of all no matter what you use be sure and have a good pressure regulator and moisture trap, and filter your paints very well, maybe with an old nylon stocking.
A success (your definition of it!) on your first model will trick you into staying with this hobby. Much more fun than failure! Good luck and enjoy.