The directions in the manual are simple and straightforward, unfortunately, they are useless. They tell the steps to changing the battery, but they don't tell one how to actually remove the air filter (for example), just above the battery.
I am changing the battery because the car hasn't been driven for two years, so "take the car to Sears" is not a solution.
I'd like to know how to remove/change/release the device that holds the air filter holder in place.
If it's like my 1999 300M I understand your frustration. I ended up taking out the air filter housing complete with the bracket that screws to the frame rail because I couldn't figure out how (or even IF) it came apart. This requires cutting the cable tie holding some harness to the back of the bracket.
With the housing and bracket out and in hand for inspection, it seems that the housing is intended to just push onto the bracket and kind of retain itself. So just pull REALLY hard to disengage the housing from the bracket. Once you have it apart, you might put some sort of lube in the rubber busing on the housing so you can pull it out with a more reasonable level of force next time.
after you get that off take the passenger tire off there is a panel there you can take off and the battery will slide out. such a pain in the butt!!!