yeah but it's a 99 n/t...not the earlier ones like you said. if i was you i would clean the oil off
and drive it for a week or 2 and then see if you can see if it still leaks...if the leak comes back from the same spot (from head/block mating surface) and drips down, then your head gasket is most likely bad. if there is oil from above the block/head mating surface and it leaks down to where you cleaned the oil before, then it's not the head gasket, you're leaking somewhere else.
also where is the leak at? do you ever spill or drip any oil onto the valve cover when you fill it up with oil? i'd still clean up where it's suspicious and drive it, check out the leak, and go from there.