Hey guys. My car has been running a little rough at idle. My car is stock with the exception of a K&N CAI. I do not have a tune or anything. I plan on replacing the fuel filter, PCV Valve, and cleaning the K&N filter this weekend. I have 103,000 miles on her and just replaced the ORIGINAL BATTERY today! 7 years out of a battery isn't bad! There is no check engine light at this time indicating any problem. So here are my questions...

Where is the PCV Valve located just to make sure?
What product do I use to clean the intake, censors, and T.B.? Brakeleen?
What else could be the culprit here? Coils? what?

I really appreciate any help you guys can be. I am really concerned about this for money is tight and I would like to figure this on my own. I am very mechanically inclined and am just looking to get ideas of what to do here!

Thanks guys!!!
TJ