Speaking as someone in the graphics industry (which makes me only the tiniest bit more qualified than my good buddy Joe Sixpack),
1) There is no computer program than can come close to the artist's renderings in the past Atlases - that's kind of like comparing the graphics in a Pixar film to the work of a great artist - Pixar films are impressive technologically, but pale artistically in comparison to even a good comic book artist, IMHO;
2) Photoshop is indeed the industry standard, but a good designer might find it easier to update things in Illustrator - kind of depends on the style of the artwork - something like the Stroke Saver yardage guides would be much easier and quicker to update in Illustrator - neither comes close to the real deal of an artist, however;
3) Even though I haven't seen your drawings, I'd guess I'd prefer them to any computer drawings. If you really want to do computer drawings, I'd go with Illustrator or CorelDRAW.
My advice would be to either spend the $$$ on a real artist, or if you are looking to save $$$, go to an art school and work with some young artists who are eager to work.