I would get your paint from a local distributor. I say this because they will be able to give you advice and tips on the paint brand you choose. I have had good luck matching WRX blue with Dupont, Standox, and PPG. Do a base/clear and not a single stage. A complete color change is a big undertaking even for the pros. It involves cutting in all the jambs/trunk/engine bay/etc. Stick with doing the exterior the same color and focus your time on prep work and learning the basics. Although, if you have your heart set on a color change by all means don't let me discourage you, and just give it your best attempt. Don't cut corners and be patient. A lot of first time painters become impatient with the time involved in painting their car and begin to rush...do not do that. Remember it is only paint, and can always be redone.