Oil Leak correction
Yes, always check your oil level when buy fill the gas tank, Keep a cardboard box under the car when parked in your garage (I hope you have one) and when you get a chance, put the car on a lift, wipe it as clean as you can and try to determine any source of leaking oil. Could be as simple as a new oil pan gasket, or as complex and expensive as a new seal.
Good luck with the car. If you need something let me know. I've parted out 4 spiders in the last two years. '79, '80 , '84 and '87.
Ray Kiszely'84 Spider Veloce