You was told your 2003 sequoia needs a cabin air filter replaced So you went to the dealer and they sold you one and told you it was behind the glove box you can't find it and its not in the manual?

you have to remove the glovebox entirely. when you do there will be a fairly large plastic box exposed. on that box you'll see a small door or hatch (approx 2"x8") there may be tabs to push in or a little tab sticking out that you can pull on to remove the door. inside is a small drawer that holds the filter. replace it the same way it came out.