Oil leak at filter

I got my oil changed at Wal-Mart last week for $11.99. I drove 11 hours up to Canada this week and while I was up there I had to park on this steep hill. When I started my car two days later to come home the “check oil” light came on. It was pouring down rain and dark and I figured that error was caused because I was parked at such a steep angle. When on level ground I power cycled the car and the light didn't come back on the whole 11 hours home. Today the light came back on so I got crawled under the car and found oil dripping everywhere. The entire underside of the car is coated with oil, even the back bumper and trunk have oil on them (I was wondering my car was accumulating dirt in the rain, but I was too tried to think anything of it.)

I put my car up on blocks and found a leak at the oil filter. I gave the filter a turn with my hand and I was able to turn it about 1/2 inch. I’m pretty sure that stopped that leak.

I put 1 1/2 quarts of oil in and that only got the dipstick up to the first of four holes, so it was really low.

So my question now it what to do about it. I got my camera out and took about 10 pictures of the leaking oil incase my engine dies and Wal-Mart needs to pay to get it fixed. I'm a mild manner kind of guy, but I guess I can go buck wild on a Wal-Mart associate to get my money back and maybe a free oil change.

As far as the engine is concerned should I be worried about possible damage?

as long as it didn't overheat, i wouldn't worry about any damage(although that's not saying none occured). but wal-mart is bad for leaving the gasket from the old filter on there if it sticks. sounds like that's what happened. i used to work at a fast lube and we had that happen probably 10x in the 2 months that i worked there with cars comeing from wal-mart.