It sounds to me like you are looking at the oil pressure sending unit. At least that is the location on the 90-93 models. After 15 years I'd be surprised if it wasn't leaking. They can be purchased at just about any auto parts store. If I remember correctly, they are less than 25 bucks. On my model (91 Accord) the sensor screw into the block (above the oil filter) and it uses an NPT thread style. That means that the more you turn it, the tighter it gets (not like a nut that will spin along the length of a bolt). The reason I mention this is because the taper of the thread is what seals the connection. It is tempting to consider putting Teflon tape on the threads to prevent future leaks but don't do it. The metal to metal contact is used for maintaining a good "ground" for the sensor. The tape will insulate the connection and the sensor won't work.
One other thing worth mentioning is that (at least on the 90-93 models) the thread designation is NOT metric like you might thing. I think it is 1/8 NPT.

I hope I'm pointing you in the right direction.
Good luck
dan