Microcontrollers need 5V or less (differs). In a car, that is usually taken care of with a voltage regulator that converts the "12V" down to 5V or whatever is needed.
Take a look at PIC BASIC (Pro) if you wanna go with a PIC or http://www.mikroe.com/en/compilers/
(which I never tried), for either PIC or AVR.
Perhaps you should seriously consider the BASIC Stamp (II), as it is probably the fastest way to a useful circuit given that you are a beginner.
Btw. Everything a BS(II) can do, a PIC and a PIC BASIC compiler can do much faster and way cheaper (at least if you use the demo or the web based compiler).
Electronics is an exact science like math and only if you get into Fuzzy Logic you should consider terms like "several". Outside the Fuzzy realm, please be more specific (like eg. "6 to 8 analog..." or whatever).