If you face both seats looking out the back window, on the right side of the head rest is the button you push in and the rest slides up and down. On the left side is the same button only under the beauty ring. You can very carefully pull the ring up and under it is the same push in type button. Pull the rest all the way up, push the left side button and it comes off with ease.
15mm
Here's how to remove it. http://www.youtube.com/watch?v=hH2qZPIK7jQ
Remove oil filler tube cap....then Wiggle and pull straight up.
With a 07 chevy cobalt key
Passenger side, underneath the glove box. You have to remove a panel from the center console.
Open up the trunk Remove the wood/carpet cover in the back. Unbolt the strap for the battery and remove it. Unbolt the bolts on the +/- sides of the battery. Remove the battery.
use a 1 and 1/4 inch socket to remove oil filter cap.
button on the dash
There are many different tire manufacturers out there. For a 2007 Chevrolet Cobalt LS, you will want the size P195/60R15.
in the trunk
It does not have one.
full instructions as to how to install cobalt halo projector headlights.