First things I'd check - oil filter adapter, and valve cover seal (in that order.)
The oil filter adapter is just in front of and above the starter - there are three orings in there.
The 88XJ should take a 5/8" wrench to pull the bolt through the adapter, and you'll find one on the bolt proper, one on the engine side of the adapter, and one under the bolt head. It's easier for us RENIX people, since we can use an open end wrench - instead of a Torx bit!
Be careful pulling the bolt, and take a moment to make sure that the threads are clean on both the thread and the hole - it's REALLY easy to break that bolt!
The valve cover is a little tickish - it's easy to crush that gasket. I usually use a cork gasket, coat it with LocTite 518 Gasket Eliminator. Tighten the bolts down with a nutdriver to contact the gasket, and go off for a sandwich and some coffee (about 20 minutes) to let everything tack up. Go back out and torque USING A TORQUE WRENCH to about 7 pound-feet (84 pound-inches) - more will likely crush the gasket and make you do it over again. Allow the sealant to cure overnight.
In either case, clean the engine well (I like LPS Precision Clean - it works quickly and well on a warmed-up engine) and run for a few minutes or so to check exactly where the leak is coming from - or you can just do both, since they're probably both due anyhow.
I don't have the part numbers for the orings handy, but you can probably find a thread with the numbers after a brief search. They're pretty cheap - and if the dealer doesn't have them, you can get them from anywhere else that has a decent selection - as long as they're either Viton or Buna-N, you're alright (check to make sure - if they don't know, check somehwere else. Most Hardware store orings are meant for water, but they often have Buna-N orings, which will work with oil.)
Again - MAKE SURE THE THREADS ARE CLEAN if you do the oil adapter, and lubricate them well. I broke one of these bolts, and I was glad to have had a spare - they're not heat treated, and the hole down the middle is farily large. They're drilled at 90* angles, about an inch from the top, which makes them fragile. BE CAREFUL!
5-90