There is no such thing as a Pre Cat/Catylitic converter, you have one on each bank most likely, some vehicles Y pipe into 1ea cat. The term pre cat is indicitave of the O2 sensor at the inlet of the Catylitic converter.
Now the big Question is.
Is your sensor bad?
Or do you have an engine issue causing the O2 sensor to read out of range?
I find it near impossible for the dealer to put a price tag on the lack of information they gave you, demand more or take your ride somewhere else.