It's never cost effective to just replace parts. You need proper diagnostic instructions. There is a company that independent auto repair shops get their information from, this same information is available inexpensively for people that work on their own cars.. The information is year make and model specific, covering repair procedures, torque specifications, fluid capacities and specifications, service bulletins, component locations, wiring diagrams ect.... Alldata is very easy to navigate http://bit.ly/AllData_Repair_Manuals_Online
This is the best information that is easy to navigate. The computer I believe is under the radio or at the right kick panel area.