First there are two primary multi meters used for basic auto repair. The first is the old "Analog" or dial type. These work great to measure just about anything you can think of on a car from resistance to voltage but on newer cars with electronics like fuel injection and the computers that control them you need to use a "Digital" one because it will measure a lot closer and give you exact readings when checking items like the O2 sensor on a fuel injected car. They usualy have a "Good range" that you should verify before replacing them and an analog one won't do it. I bought a small one from Radio Shack for around $ 24.00 and it works great but I still like to use the old analog one for just checking stuff like voltage and continuity of wires and such.
Check your local auto parts and then check Radio Shack and see which way you want to go and good luck.. hope you don't have to use it much as that means you are trouble free !
Dennis