You will need to use a scan tool to retrieve the fault codes stored in computer memory to give some basis for starting diagnosis... Autozone will pull them for you for free, but dont buy any parts at that time (the counter guys have zero training and just want to push parts; they have no idea how to diagnose problems and are wrong more often than not).
If you can get the failure codes, post them and I'll see what I can do to help you out...