Help in replacing drivetrain

I have a Schwinn Crisscross ATB circa 1992 that has Suntour deraillers,
shifters and cassette along with Joytech hubs. Cleaning the hubs revealed
severe pitting in the cones and I'm having a hard time finding the correct
replacement pieces. In addition the cassete cogs on the smaller gears skip
badly and I assume the chain needs replacing as well. I guess I just need
to replace the entire drivetrain including the hubs and wheels!? It looks
to be getting pricey quickly! Is this the most cost effective option?

If so, is there a guide/tips to replacing a drivetrain, including matching
wheels and hubs/freewheel, crank, etc? I'm lost as to finding what hubs
work with which cassettes which work with which derailler which work with
which shifters etc. By the way the shifters are NOS Suntours - can they be
reused? I don't want top shelf components as this bike is meant more as a
beater and experimention type thing.

Cheers!
Duke