The answer is YES... you can do this yourself.. and expect great results... the time investment depends on your level of skill, but even noobs can get good results right out of thegate. The equipment is where most people get into trouble. There's no "single post" explanation of how to paint a car by yourself, my DVDs are over an hour in length, filled with condensed info. and each deals with a specific segment of the process. My participation on this website is to help with these types of questions, so lets adress the air compressor;
You need a minimum of a 5 HP 60 gallon tank compressor with at least 11 CFM of air delivery. Dont pay attention to pressure; it doesnt matter anymore, it's all about CFM and air volume, and to atomize todays paints and materials, you need HVLP guns and a good compressor with a high duty cycle. you also need to outfit the compressor with good driers and moisture separators... and they need to be plumbed in a way that they actually work ( at least 20 feet of pipe from the compressor manifold) Your airline needs to be at the very least 3/4 ID to facilitate the CFM delivery to the gun.
There are probably guys who'll beat the crap out of this post, and say that they painted a tractor trailer with an airbrush compressor and it turned out great... the truth is sometimes you can get away with things that are typically not the best setup. but if you think about your compressor as the heart of the shop ( it is...) and build everything off of that, you can eliminate a ton of problems before they're actually problems in your paintjob.
Yes, you need to invest some cashola in equipment, but you dont need to go crazy... this can be affordable, but depending on the type and brand of paint and primer that you buy, you can easily spend what it costs for a good air delivery system on a single paintjob, and to have it blow up in your face because of solvent trapping, water in the lines, and low pressure, eventually having to spend more cashola to repair things.... that puts a real bad tase in your mouth that doesnt need to be.
Dont neglect safety!!!!! these chemicals are concentrated and dangerous if you're careless.... be responsible for you and others around you.. no joke.
Is DIY dead? hell no! but it does take a little more time and money investment and practice than it used to.
Dont be intimidated by this process... but be realistic about what it takes to
do it right.