Is it crucial that you learn on someone elses car? You said your dad knows how to drive a manual, so ask him if when you find one, he could take a day the weekend after, or when, you bring the car home, to take you somewhere safe and teach you how to drive it. The Zetec and the Duratec are excellent engines, and with proper care, can, and do for some people on here, last over 200K. 100k shouldn't be a problem, but you have to think that a car that at the least is 6 years old, and has 100k, will more than likely need some maintenance, and some new parts. Also, take the car for a test drive and visually inspect it, look at the brakes, tire tread, visually inspect the engine, check the trunk for a mildew smell (leaking water), etc. Take a couple of them for a drive, and maybe you'll find just the one you want. Have you checked
www.autotrader.com for any yet? That's how I found mine.
