I changed the oil recently on my 99 and I noticed what appeared to be old oil residue that had dried up. It looks like something has poured out and then it stopped thus you could see a faded line of where it has dripped too.

Anyway, looking around I noticed the plug in the pictures below about half of the way sticking up in the air. I can push it right back in, and it comes out without any resistance. I think this is an okygen sensor of some kind? There appears to be a rubber grommit that holds it in place but it must need replaced. Any ideas of what part I need to order to do this myself?

 

Thats the PCV. (positive crank ventilation) I'm sure you can get the gromet at a dealership for a few bucks.

 

Thats the PVC 100% and it pops out very easily. since you know where it is, check it to see if it needs to be replaced.

 

I got a new gromit and replaced it not the PVC is good to go.
Thanks!