That really depends, let me be completely honest. I haven't been in the aftermarket iPhone screen game for a long long time lol, the last time I was connected to that whole "scene" was in the iPhone 4s days.
Granted it's still the same, you're going to have a couple options. There should be dirt cheap display assembleys around for less than 40 bucks. The thing I ran into with these screens is the oleohobic coating was ALWAYS bad on them, and the panels on them were always terrible.
Your other option is to find a dirt cheap "for parts" iPhone 6, and rip the assembly out of that one. At least this way you'll probably get an oem assembly.
I can't speak for the services people provide, but if you hire somebody they'll probably charge you about $100 and I doubt they'll toss you an oem assembly.
I'd say do some research, if you choose to have somebody do it for you, make sure they're giving you genuine parts. My plan of attack would me resell the repaired phone and buy a new in box old device with the money you get. It's annoying but you aren't fumbling around with crap iPhone parts.