Cadillac 2002 DeVille Owner's Manual page 330

2. Then, insert a tool behind the push pin located on the
inboard side of the air filter compartment to carefully
pry the pin out.
6-20
3. To remove the air filter, insert a tool between the air
filter and the compartment wall on the outboard side
of the vehicle. Then, push in to flatten the pin
holding the air filter in place. Gently remove the air
filter and any loose debris that may be inside the air
filter compartment.
4. Insert the new air filter by pushing until you hear a
click. Then, reinstall the push pin and snap the cover
into place.