installing factory sub system in LT
 

How hard would it be to install the 10" pioneer that came factory into a car without it, and also what all is needed?

Not sure? I know you will have to run all the power and rca wires to it but dont know how the factory amp will work with it? it wouldnt be a bad idea to use the shell and add a better 8" sub like a JL audio then run a external amp to it. that way its out of the way looking factory but sounding a heck of alot better.

There are no power and rca wires going to the sub on the factory system. The amp is up under the dash so the only thing going to the factory sub is speaker wire.

In order to add the factory sub you'd have to add the factory amp and a factory head unit (or any amp and any head unit) for cars that had the sub installed from the factory since those HUs have low level outputs instead of speaker level outputs.