I have a 2002 2dr Accent Hatchback. The passenger side seat belt "spool"
(near the floor - behind the interior panel of the back seat)is messed up.
When someone puts on the seatbelt,sometimes it locks and won't release. It
just keeps getting tighter and tighter. (I know it is designed to "lock up"
in the event of a sudden movement - but then after that it won't release)
Seems like a ratcheting feature is broken. Is this an expensive repair??
Thanks for any help.

That depends on what you call expensive. Very rough estimate, $300 to
$400 for new seat belt and retractor assembly.

I assume this is a dealer part (or junkyard)??
Is it difficult to replace???

I wouldn't have any problem with a junk yard seat belt as long is it was
operating properly and wasn't worn in a collision. Your call whether you
do new or used.

In most cases, the seat belts are reasonable simple (again, depending on
your definition of "difficult) to replace. They anchor with a bolt under
the rear seat, and you'll typically have to pull a couple trim pieces to
get to the retractor end.

Thanks,
I will give it a try!!!