Brought my car in to get fixed and got it back and its horrible. what do i do?

My car has caused me hell. its a 93 mercury sable. i dont have the money to get a new one, and my dad isgoing through stress with money. we have spent 800 dollars once month, 800 the next.. two months later, 800 again. it has happened countless number of time! we dont know a reliable mechanic who wont gip us, or even fix the car right! the last thing that went wrong, my dad had the choice of renting or leasing a car, or fixing this piece of crap again. he doesnt wantt o deal with it, as we are also trying to sell our house. SOOO he mistakenly chose to fix it. came out to eight undred again. and once again, guess what? A NEW problem is there im feeling, plus the old problems are all there and even worse. the only thing that was fixed was the steering wheel stopped shaking when i brake. that was fixed. NOW, how do i approach this? we have the receipt, what can ido about this? me or my family know nothing about cars!