2005 Dodge Magnum engine problems or tranny? Your guess or

Hi, i've had problems since day 2 of owning this dodge, My cd player has a mind of it's own it comes on when it gets ready, when I open the doors, trunk or whatever, it makes a loud clicking noise, with or with out a cd inside the player? Could this be electrical problems, or what? Also poor acceleration which I was told because of o2 sensor, repaired/replaced. Engine still dragging, poor gas mileage, Please help me I have cried many days about this darn car, I feel that I can trust no one to give me a fair price and good mechanical work.