I have a 1980 Datsun pickup that's been a jewel of a pickup UNTIL MY
KID started driving it... :-)

The clutch is suddenly slipping pretty badly even though it appears to
have good pedal action/play (you wouldn't guess there would be an
issue based on the clutch pedal play).  

I attribute this issue to either oil having gotten onto the clutch
disk OR some issue with the hydraulic clutch mechanism.

It's had a small oil leak for sometime now.   The kid at Walmart who
looked at it from the pit underneath thought it was a rear main seal
leaking which might explain oil on the clutch disk causing the
slippage.

I've changed a lot of clutches myself years ago in my hotrods but have
never done anything like this on a Datsun so am wondering if these
little pickups are difficult to work on, whether 'special' tools are
involved and in general, if it's something I should find an
experienced 'datsun' mechanic to work on (having no idea what the
level of difficulty might be on a little foreign job.  TIA for any
replies...