How do I replace the screen?

@volchokthegreat those guides have not yet been created by neither iFixit nor any of the users on iFixit. So, you are our pathfinder on this. I would suggest this teardown window It should get you there. Just take your time and be organized and I think you'll get it. While you are doing so, take plenty of good pictures and create a guide Create a new Guide - iFixit for the rest of us. That way, the next person that is in the same predicament as you currently are, will have a reliable source to turn to. As for parts, it does not look like iFixit has that screen. I would do an online search and pick a seller that has good feedback and good customer service.

Of course, you can always try OnePlus itself. For your model the price is listed as $250USD