Best places to buy parts for 6P?

I am thinking of replacing my screen/ digitizer, and front camera. There are a lot of different vendors to use with a great price variation- screens seem to be $60-$120.

How do you know if parts are the same quality as original? It's even confusing as to whether parts being sold are new or refurbished.

So where do you buy from that is good quality yet not top priced?

Thanks...