Thanks for the input everyone! I'm happy to report I was just a bit too cautious when replacing the airbox cover. I looked at the rear of the cover from the passenger side and I could see a 1/4" space above the throttle body. A firm push on the back corner popped it into place. All is well. It was the first time I've had the cover off so wasn't sure how much pressure to apply.

Oil and air filter change complete and I connected the window washer nozzle that had come off. Now she needs a bath and a nice drive!

I did notice a bit of white smoke from the exhaust when I returned from a little test drive around the block. Also, it could be my imagination but it sounds like the engine is louder (engine sound from bay, not from exhaust). When I bought this car last year the dealer had changed the oil (obviously not the air filters!!!) and the sticker they put in the windshield said 'Penzoil - 5W-30'. I've done two oil changes since then with Mobil 1 0W-40. Does the thinner oil allow more lifter, cam, crank "noise"? Engine runs great and I've never had any issue with this car since I've had it.