2003 Elantra Stiff Shifter

My car was sitting for about 1.5 weeks and now all of a sudden its hard to move the shifter between gears. Its an automatic. I have to put it in neutral to start it. It wont start in park. I called hyundai and they said its probally the linkage and that i should grease it, but i dont know how to do this. Can anyone help me? Some one told me to remove the plastic box that the air filter fits into, so i did that but im not sure what im suppose to grease.