Slight smell of oil

Extended warranties generally cover "internally lubricated parts". In other words, you aren't very likely to use that warranty unless there's a catastrophic failure. The first thing to do is look for signs of oil leaking from the engine. If it's bad enough it will drip onto the ground where you park.

If repairs are needed and you get the all too common, "what you need isn't covered" reply, cash the extended warranty in for a partial refund and use that money to pay for the repair.

Ahh. Very often during an oil change, oil will run out of the filter fitting and collect in hidden places. That residue is harmless and will vaporize eventually and blow away. Some mechanics will take the time to look for that oil and wipe it off but that takes time. More customers get angry when an oil change takes a few minutes more than scheduled than from the oil smell, so the emphasis is usually on "fast", not "tidy".

On some cars and trucks, when the filter is removed, that oil runs into a cross member or is hidden behind an engine mount, starter, or something else that makes it almost impossible to clean off. In cases like that, and with your car, be sure the rubber seal is in place at the rear edge of the hood. If it's missing or has gaps, fumes from the engine area can be drawn through the fresh air opening in front of the windshield. Years ago that weatherstrip was attached with plastic pins. Installing those are WAY too labor-intensive today so that seal is typically held on with double-sided tape. With a little pressure, those parts often walk around over time. Body shops attach them with adhesive which holds much better.

Also check the AC condensate drain tube. There should be a 4" rubber hose with a 90 degree bend hanging down from the passenger side of the firewall under the hood. That hose is molded into a thin slot on the end to reduce air blowing in. A lot of air will come in if that hose fell off.