I'm with you and... do your own(and spend the rest on diesel fuel!)
I have pulled to the back of Auto Zones and Advanced and changed my oil before. I told the manager or store clerk what I was doing and they have never told me no. Just buy your oil and filter from them and they don't care, just make sure you don't leave them a mess to clean up. Even changed oil in the parking lot of a Wal-Mart once after 10:00 pm, how much light you need to unscrew a plug and filter, drained into loaner oil pan from Auto Zone, then took pan and all back next morning, $100.00 plus bucks saved.