Stands for positive crankcase ventillation and as the name implies, it works with other components to vent pressure from the crankcase. While the engine is running, blowby makes it past the piston rings and into the voids in the engine (oil pan, valve covers, etc). This pressure and gas has to go somewhere so, the pcv valve allows it to be drawn into the intake tract so the engine burns it (as opposed to venting it into the air). It is located in the upper intake, center, all the way in the back against the firewall. It is not too bad to change but is easier on many other cars. Hope this helps.
You have a vacuum line from the PCV valve that is located in your intake manifold to the underside of your upper intake. There are no lines in the inside of the engine, just many passages that air can move around.