Wanted to share my bottom screen replacement experience with yall.
My son's DSL bottom screen was smashed, LCD not touchscreen. So, I ordered one and replaced it. After making the replacement following the YouTube video, the unit no longer powered on.
I then came back here and began reading more forum posts. Then I was convinced I had most likely fried the motherboard, because I too had not transferred the foam insulaion from the old screen. I discovered this on trash day after the truck had come and taken away all the trash, including the old screen with the foam still on it.

I also saw that I could have just blown a fuse, but I was frustrated with messing with the tiny thing several times in two days, so I just set it aside for about a week.
My son decided he wanted to sell it on eBay as a parts unit. I started to make the listing for him, then decided maybe I should borrow a volt meter and try to check the fuses before letting it go for $10-20.
So I got a volt meter from a friend last night, and cracked the stupid DS open one more time this afternoon. I also hunted up some foam tape from out in the garage. (What I used happened to be foam tape kitchen cabinet door bumpers, so it was a little thick but it's what I had.)
I checked continuity on both fuses, though it ook me a while to find F2, and both indicated that they were still intact. Now I'm really thinking fried MB. But I reassembled it, and test powered the unit, and much to my surprise it came on!!!!
Wish I knew what I did, but mostly I'm just glad I'm not buying a new unit. Good luck to the rest of you DIY'ers, and don't give up too quickly on these pesky things.