4 years old, 7500 miles, 3 oil changes. Should I buy? Is there a way to inspect?

Bing: Yes. Bumper to bumper for 60 months. The extended power train warranty 120 months/100,000 miles “does not transfer to subsequent owners”. From my 2010 owners manual.

There is no way that the manufacturer can require you to have records from before you bought the car. There is nothing for a mechanic to check regarding 3 oil changes at 12000 miles.