I have had my S21 ultra since the start (I hope this post is ok)

I have had my S21 Ultra since the week of it's release. It's the first phone I have ever paid for in full up front. It would be understatement when I say I effing LOVE my phone. It has been cared for like a child. It has only briefly and on rare occasions left the otterbox I got to take care of it. I have never even dropped it. I am not exaggerating. Recently, a friend of mine took it out of their vehicle while we were packing to leave an outdoor area that we were hanging out at and he placed it on the roof of his vehicle and forgot. Already long story short, it fell off and was run over.(maybe more than once as I didn't find it until 2hrs later with the find my phone) IT STILL WORKS. The screen is really bad though. I want to replace the screen and probably have the general know how to do it myself. Does anyone have any advice? Any direction they may be able to point me in that would be cost effective? I have done some research but I am not good at it. I THANK YOU IN ADVANCE! I hope someone can help. <3