The spec fork on that was the Answer Manitou Axel Super - information here
From the 2003 Axel user manual....
CHECKING OIL LEVEL IMPORTANT: Setting the proper oil level in your
Fluid Flow damped fork is critical. Fluid Flow damping is located in
the right leg of your Manitou AXEL fork. Not enough oil will allow
foaming and reduce the performance. Too much oil will restrict travel
and may cause damage to the system and create an unsafe riding
condition. Finish reading this entire section prior to altering the
oil level. To check the oil level on the Manitou AXEL, remove the
compression assembly located in the top of the right leg (as you are
looking at the fork from the rider’s position). Leave the left side
spring stack in place to keep the fork fully extended. Use a tape
measure or “dip stick” to measure from the top of the fork crown down
to where the oil sits (Figure 2). The oil level for the Manitou AXEL
should be per following table. Fork Model Oil Level Manitou AXEL
115-125 mm (4.5-4.9”) NOTE: Use SAE 5WT fork oil suspension fluid
Forks need regular servicing - anything as often as every 25 hours
with seal replacement commonly being recommended at 100hours riding (I
think Manitou had relatibvely long service intervals . Seal
replacement and lower leg service is not too hard, but is a bigger job
than many owners are prepared to tackle themselves. A shop secive
with seal replacement will be around $US100 (various with you location
in the world).
The seals have gone - possible just from old age and wear. Given the age and value of the bike, its likely not worth the cost of new seals, especially if you are getting a shop to do it. If you don;t want to pull the fork apart, replacing the oil is straight forward, but I would be tempted to do a lower leg service and then top up the oil regularly.
The oil leaking is a messy problem, but no causing functional issues as long as there is oil to leak out. If the leak stops its time to worry.