OBD-II codes PO171 and PO340

I have a 2003 Dodge Neon with a 4 cylinder 2.0 L engine and approx. 64K miles. The check engine light came on and when I was at Jiffy Lube I had them run a diagnostic that came back PO171 (with a notation that said "System too lean (Bank 1)") and PO340 (with a notation that said "Camshaft Position Sensor A - Bank 1 Circuit Malfunction"). I think I've figured out that PO171 has something to do with the air/fuel ratio (or could, as PO171 seems like a catchall for a lot of things related to the ratio). I'm not sure where the best place to start is. Is there a mass air flow sensor that needs to be cleaned or replaced? Or would the manifold absolute pressure sensor be involved? And does the other code mean that I need to replace the camshaft position sensor? Are these problems related to each other and will fixing one fix the other without further repairs?

There are a few things that seem completely unrelated to me, but I'll include here, because I don't really know. We've been rear ended a few times in the last 6 months, but haven't sustained much damage or even replaced the rear bumper. Also, about 4 months ago the engine light came on while I was taking a beginners auto repair class. The instructor checked it and cleared the code and said it involved the EVAP system, but he didn't elaborate and the check engine light didn't come on again until recently. I'd really appreciate some help with figuring this out.

Thanks!