It depends on the year.

1994 was in the Engine bay driver side, nicely protected.

1997 is UNDER the trunk, near the passenger side rear wheel, getting filled with gravel and road-salt.

(One of many things that the 1994 did way better than 1997).

There is no mention of oil. In dis-assembling and re-assembling the cylinder head, the only lubrication mentioned is an O-ring at the top of the cylinder head to be lubricated with "petroleum jelly or equivalent".

It appears that the only maintenance required seems to be if a leak is discovered, in which case the solutions appear to be::
1. make sure hoses are not leaking.
2, make sure the struts themselves, are not leaking.
3. Check torque on compressor bolts. (35 lb-in)
4. Replace compressor head.
5. Replace air dryer (the can perpendicular to the finned compressor head)

Other than that, if it is not working at all, then the cover may be taken off the motor part, and inspect that the motor'* brushes seem to be making contact correctly and no debris jamming the motor. Beyond that, it says: "replace", of course.