While I never did the 6+, I replaced my own iPhone 6 screen and while there were a lot of little things to be careful about, it was pretty damn easy. It probably took me 45 minutes total.
This was the one I ordered:
https://www.amazon.com/gp/product/B073N6T92B/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
It came with all of the tools necessary too.
If you do get one, I'd get one that costs like $10-$15 more with good reviews over the ones that are a bit cheaper with mediocre reviews. If you read the cheaper reviews, those appear to have some where the screen has issues after installation. After doing all of the work, I'd hate for stuff to not work.