general problems of the 2006 Hyundai Tucson

I purchased my 2006 GLS v-6 Hyundai Tucson October 28, 2008. Right after we purchased it we noticed that driving up or down slopes turned off the vehicle. We took it back to the dealership and they had the gas cap replaced and was told that it solved the problem. Then about a week later the check engine light came on. We took it back into the shop and it was the pressure in the gas pump that time. Then the light came back on and we took it to Hyundai. They turned off the light but never found the reason as to why it was coming on. Although they did not hesitate to try to sell us services that had nothing to do with the check engine light coming on or the car just shutting off. To this day the check engine light has been on. Hyundai has offered to shut it off but whats the sense in shutting it off when the problem is still there? now the car just stops. . . . I was driving back from san juan capistrano to riverside, CA and we were in traffic about 50-60 miles and the car just shut off. . . . Since then the car does it regularly sometime 4-5 times. We called Hyundai and they suggest replacing the gas cap again. . Im not a mechanic but I think I understand that this is not a gas cap replacement issue. Im scared to drive the car. I've tried turning in the car but my credit is not good enough because I have 2 car loans. Hyundai kept sending me papers and calling me saying that they would like to buy it back but it was just a scam to get me in to try to purchase another vehicle. They do not stand behind their cars or try to solve the problems at hand. Also when I purchased the vehicle it was under 100, 000 and I asked Hyundai what were my warranties and was told that since I bought it from a used car lot that the warranties are void. I am paying after finance charges. . . $16,144. 34. I expect this car to last me more than a year or 2.