I'm a young adult just out of high school.

Hi, I'm a young adult just out of high school looking for a very cheap used car. I understand when you go cheap your looking for problems. I don't mind spending money on the car, I just don't want to keep throwing my money into an endless pit when I don't make a whole lot to begin with. As a professional what would you suggest? I'm looking at a 2000 Monte Carlo SS for $500. Interier is good/fair, and exterier is fair (some dents, and few areas are begging to rust). Millage, 265x. Runs, but the check engine light, oil light, and abs light is on, meaning the car failed inspection. The car also doesn't go into first gear (automatic btw), and the over drive doesn't work. The private seller told me its the valve body on the bottom of the transmission. Would replacing the valve body fix these problems? I just want something to last me a few years so I can save for something better, w/o wasting all my money on this car. In your opinion, is it worth it? Thanks!