When you buy an oil filter cartridge, even from a low quality manfacturer like fram, they include an O-ring for the screw top plate for the oil filter housing, as well as a new oil drain plug gasket.
If you went to a quickie lube and they supplied the filter, it's possible the lube person didn't know what or why there was a large o-ring in the box and didn't change it out.
I'd go down to your local auto parts store, just buy a new filter, make sure the o-ring is in there, and just pop the lid on the housing, replace the o-ring AND filter, while you're in there, it's easy to do and you don't need to climb under the car.
as for the gunk, you can also buy a can of foamy engine bright, it's made by Gunk, or any spray on degreaser. spray the area and wait a few minutes then hose it down gently with water. It'll be like it never happened.