94 civic lx seat woes

The driver's seat in my 1994 Civic started squeaking from the right
hinge a while ago. Recently it's started sinking on that side, to the
point where you're sitting pretty cockeyed while driving. To make
matters worse, when I took the seat out to investigate, the rear left
bolt came out as if there was a nut on the other side, and now I notice
there's a crack in the floor coming out of the bolt hole going
who-knows how far. The bolt now has nothing to thread into, as
presumably the nut on the other side has fallen off somewhere into the
floor.

So, my questions a should I replace the bushings in that one hinge
or just replace the whole seat? And when I go to do this, is there an
easy way to fix the problem with the mounting bolt? I can't find any
obvious way to get to the backside of the floor where the seat mounts.

Thanks in advance for any help,

Isaac