I wouldn't mess with the oil cooler lines either. If you change the oil from here on out at regular intervals, the little bit that's left won't hurt anything. Get the two little rubber O rings for the oil filter and replace them too. Use a good OE filter like a Mann, Hengst or Mahle/Knecht. Don't buy a cheap McParts filter. The OE filter ought to come with the big O ring for the filter canister and a new washer for the drain plug.

Len