what is your total budget?
Having a set budget will give you a lifle line from going too deep into the rabbit hole!!
Agree with
@LDP on getting the best you can afford..100-200 yards is going to need quality glass( not necessarily expensive) and magnification
Pesonally, i do not sell my rifles that shoot well. I have the notion in my head(right or wrong) that most do the same. If it shoots well, they keep it, if not...sell.
So i would say buy new. But that's just my opinion.
If you are shooting over 100 ...you're probably shooting slugs ..that's a entirely different rabbit hole that i am still navigating
Do you have the support equipment ...a tank and a place to fill, or a compressor. Bags or bipod to shoot off. cleaning and maintenance.
Give these guys a $$$ amount and they will be happy to spend it for you