I bought a cracked phone online for significantly cheaper ($40 vs $120+) with the intention on buying a screen and replacing it myself.
The repair went much more smoothly than I thought it would. I have replaced a number of iPhone 4/s screens, which were significantly more difficult. The screen from iFixit worked and fit perfectly! No issues post repair.
If you're looking into buying an iPhone, I consider buying a cracked one online and replacing the screen. It's significantly cheaper, so long as everything else works okay and you're certain of that.
Be careful plugging in the components into the motherboard. If they aren't clipping in, don't force it. Reposition it and try again. You definitely don't want to bend any tiny pins.
Definitely shell out the extra money to get all the components already on the new screen, as that saves a lot of time.
The screws are UNBELIEVABLY tiny and are much easier coming out than going in. I suggest using a better screwdriver than the ones typical screens come with, as they would magnetize better to a better screwdriver and they will be significantly easier to get back in their respective holes.