My Santa Fe has 301,000 miles with the original engine and transmission.

An oil change should not cause this. Maybe it was there prior and you didn't notice. Maybe the oil cap is loose. 301,000 miles, pretty good. It doesn't owe you anything. If it runs, it's work something. Get it checked before you graveyard it.

Have a trusted shop clean and verify the source of leak(s) , then decide.

You can add oil fairly cheaply if the leak isn't too much. If you can clean off your engine(simple green) you might have a chance to find out where the leak is coming from.