There are 3 hoses that exit just behind and below the engine/transmission on the left hand side. One is the tank vent and the other 2 are air box drain hoses, one for each side of the air box. These are supposed to be plugged.
What probably happened is that one or both plugs might have been knocked out of their respective hoses, probably while unloading from the trailer. This would allow any accumulation of oil from the crankcase vent which goes to the air box to drain out. Some accumulation of oil is normal. I normally check mine at oil changes.
Another issue could be that the engine crankcase vent hose has disconnected from the air box and some residual oil is coming out of it. Just plug it back in.
This
HOSE link shows the hoses. Note the two number 11 hoses with plugs and number 15 hose.
