Think of the computer as a central hub, and imagine a profile for every device that data goes through. A monitor profile for everything displayed, a printer profile for everything printed, a scanner profile for everything coming in from the scanner, etc. The profiles mearly translate anything weird with the given device to take it to common ground before being passed on. If you mearly use a monitor profile, that's fine so long as you don't plan on printing. If you skip the printer profile you will see the quirks of the printer, uncorrected. That being said, all but the pros can use the standard printer profiles, they are very close. Also, most major online printers provide profiles for thier machines that you can download. I send all my stuff out and use the profiles provided, with perfect results. I print proofs with my printer at home just as a rough estimate, yet it's still remarkably accurate with the stock profile.
I use the eye-one display2 calibrator/profiler. It does an exceptional job on my equipment, especially my 24" Dell. It was $220 from chromix.