Well, it's always nice to have a good scan to start with, but there are a FEW tricks that you can use to res-up pictures.
1. Start with a low-dpi image.
2. Run filter, gausian blur until you don't see to many artifacts (funny JPG type dots and weird colors) and you still have fairly crisp edges.
3. Up-res as desired.
4. Run filter, sharpen, unsharp mask... play with the settings until you bring more crispness back to the lines, without generating new artifacts, or bringing back the old ones.
That technique can really stretch a lot of images well past their realistic DPI.
If you would like to see an example of this technique, go to
http://homepage.mac.com/mahuti/vpics.jpg Be warned, it's about 500 K image. The pic above was scaled up to 300 dpi at 22 x 36.
The top image shows with technique, bottom shows scaled up without. The top image is far from perfect, but is (in my opinion) superior to the one below. With a better initial scan, the more you can upres later. With ANY scan of a magazine, or other printed material, there is only so much you can scan before you start to see the stochastic printing dots, and you have to use this technique to remove those dots later.
Soo.. 1. Answered above (sort of) it takes some experimentation to get acceptable results. You should use Photoshop. It's a raster-based image program... deals with DPI. Illustrator is for vector (line art) It has some use with images, but that is really Photoshop's forte.
2. a. pull it off of the background. b. put a non-black line around it (like an outline or a circle) c. print it on paper big enough to cover the whole cab.
personally, I'd add some extra art around it (2b) Plenty of arcade cabs you could use as reference.