Not all can handle the power of the zx14. I'm 5'4" 43kg, and i can handle it but my friend that's 5'9" 57kg coudln't.Welcome Cliff
Congrats on your recent acquisition :crazyloco
So did the previous owner find it too much?
Not done an exhaust swap on a 14 but on the 1100 Geep you have to remove lower fairings, oil cooler (swing out of way), drain & remove radiator, so must be similar on 14.
Make sure you have the exhaust port gaskets & joint paste before you start & do a trial fit to make sure everything goes together properly. If you've not fitted a system before it is fairly easy DIY.
Can't help on power gains but Yoshi site should have info.