new crankset needed

I have an '94 Giant ATX 870. Lately more and more has needed replacing: new back wheel, new bottom bracket. And now i need a new crankset.
edit: oops yeah 94 not 84 :)

This happened because my pedals were falling apart and in the course of trying to get them off, the guy told me the drive side pedal was rusted on after so long.
So they got it out and apparently it took a long time but now there is no threading on the crank for a pedal.

At this point i think, i can replace the crank and rings but seriously what else will go wrong. Already sometimes I have to push several times on the front shifter to get the front deraillur to move up a gear. This could be the cable stretching or the shifter wearing out. It hasn't happened for awhile but I can't reproduce it in front of anyone anyway.

Also I thought i read you can't just replace one you really should replace the rear sprocket too? ugh.

not sure if i can or should replace just the crankset (about $60 in parts) or think about rebuilding it all. Or just get a new bike. I was looking at road bikes but was going to keep this one for winter. I have nostalgia for it which is interfering in making decisions :)