Price to sell my car that breaks down?

I'm 17 and about a year ago my mom (she's a single parent) bought me a 2001 Ford Focus from this mechanic off of Craigslist. She paid $2000 for it. He seemed like a reliable and trustworthy guy, she bought the car at his repair shop. Anyway, a few weeks after I had the car it broke down in the middle of a busy road. I was waiting at the stop light and it just completely shut down. After a few tries of turning the key it start again, but it really scared me. Didn't happen for another 2 or so months, but it kept doing the same thing at the most random times. One day it completely shut down and would not start no matter what I did, and the engine made weird noises, so I had to get it towed. We took it to a mechanic that is really respected in my area and he told us as it was: "It could break down for good a year from now, or tomorrow. There's this part that would hold it out for a longer time, but it's $500, and I know you guys don't have that kind of money." Even if we did get the part, my mom and myself wouldn't feel comfortable having me drive the car on highways and busy streets. Anyway, the mechanic did some other work on it for no charge but after a few weeks it did the same thing (where it would stall but start again). It did this like 5 more times until we had enough. So, what I'm asking is, how should we go about selling it? How much? We need to get something out of it, because my mom works really hard and can't afford to lose all the money she spent on it. Thank you.
Added (1). Also, what are good, RELIABLE cars for about $2000-$2500? I know there aren't many for that cheap, but that's about all we can spend at the moment. $2500 is the maximum. Thank you!

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