Sounds like a CJ-5. The clutch is easy with a standard tool box. Drop the driveshafts, unbolt the tranny and transfer case as one from the engine, pull the tranny back to expose the clutch. If the flywheel looks okay, replace the clutch, throwout bearing (and pilot bearing if it has it, I'm used to the 258 so have no idea), and pressure plate. Put the tranny back on and hook up the driveshafts.
There are some other things you'd need to do such as pulling the shifter mechanisms and clutch release mechanism, but a Chilton's or Hayne's manual will do you wonders.
I would venture that the 304 alone (if it runs) is worth the $350 he's asking. If the tub is intact it's CERTAINLY worth that and more. Check this thread
for what I mean. If I lived closer I'd be chomping at the bit to buy it out from under you!!
As for what they ran for driveline components, they were as varied as they come. My 74 had a 258 I-6 with a 3 speed and a 5 position transfer case (4Hi-2Hi-N-2Lo-4Lo) which I found unique. As far as I know they came with 3spd, 4spd and 5spd manuals and 3spd autos. They also came with 151 I-4's, s different I-6's and two different V-8's. The axles were just as varied as well. There were also short and long wheelbase chassis. Buying a CJ is like getting a Christmas present. You can own it for a couple years and still be finding stuff out about that you never knew.