Thanks for providing that info.So far in this thread, nobody has explained the usual reason you have oil on the floor after a GT350 oil change.
The underbody at the front has an aero extension back from the splitter that ends just forward of the drain plug. Now, the drain plug is a plastic unit that turns 1/3 of a turn to remove, 1/3 of a turn to lock back in. Leaks are rare.
However, oil gets on the splitter aero undertray when they take the filter off. It has a removable port in it to service the filter, but oil goes everywhere when you unscrew the filter housing. You lose about 1/2 quart of oil and if you don't take a lot of care, it ends up in a pool on the top of the undertray. And then it drips on the ground under the car until it's all gone, which can take a while.
So, the oil you're seeing, so long as there isn't an actual leak, is from changing the filter. Give it a couple of weeks and it'll be gone, or have the dealer clean up the mess. Either way, it's only temporary.