Exhaust
Assuming the exhaust components fits up to each other, you should be able to bolt it up (I'm pretty sure the Borla cat back system only has 1 muffler BTW).
You will not need to retune your car after doing full exhaust. I ran around on full bolt-ons for a long time back in the day without any tuning. Your PCM will learn and adjust on the small things like bolt-ons. Its not until you start opening up and modifying the motor that you'll need to have the PCM re-tuned.

