When you get the new one, the easiest way to replace them is to undo all the clamping points for the old one then tape a stout cord or wire onto the carb end of the old cable.  Pull the old one out from inside the car, then tape the new one to the cord you've just pulled through from the engine bay and pull it back to the carb.  Job done no hassles trying to route the new cable where it should be.

Really no issues with this cable replacement. Pretty easy job, really. Just unhook both ends, mash the plastic "locks" in a bit to get the cable loose from the bracket at the carb, and the firewall, and pull it out. Reassemble in reverse!(rinse and repeat)

Don't know if your car has the cable attached at the firewall with a bolt/screw, or just the plastic housing, tho. Either way, it's still a pretty simple deal.
You might check with your local Chevy dealer. That cable may still be available from GM. If not, any of the vendors should have the same cable, so it would simply be a matter of price as far as who to get it from.

Thanks Fellers!!!!