i'd be very surprised if you could get this job done for 100.00. to do it correctly the components would need to be removed and the frame stripped, prepped, and painted. and if you are going to strip the frame you might as well replace any worn parts or cables when you rebuild after painting. lube and grease as needed. so consider it a total rebuilld of the bike.
if you have the tools and can already can do that yourself, than you'll save some money. you could try borrowing tools too. but buying them can get expensive and unless you use them all the time, probably not worth the expense.
after the strip, the frame would need to be prepped. i beleive "beadblasting" (using tiny glass, plastic, beads) is the recommended blasting media for aluminum. using anything agresseive can do a problem to frame integrity so i wouldnt turn just anyone loose with a home sandblaster on an aluminum bike frame.
then powdercoat or paint -automotive paint w/clear coats is pretty durable. the better paints are expensive and toxic to spray so consider a pro for that job unless you have all the proper safety equip.
at best, i'd say close to 100.00 for each of those stages. perhaps your experiences will be different.
if you are on a budget or just don't want to spend the money on non gun items, id encourage you not to repaint. as aluminum, it's not going to rust. or how does the idea of touching up the bad areas in some creative way sound? with a contrasting or complementay color, you could paint those areas yourself -little X's, tiger stripes, dots, whatever...you get the idea.