You can buy Nexus 7 screens from here
, probably best to get the one with the digitizer here
. Firstly less work and secondly, if you don't buy the digitiser you may find it damaged from the fall.
I'm not sure whether you would be confident tearing into your device but the only other alternative would be to send the device off to Asus. From what I've read that is going to cost a whole lot more.
Other users on here have successfully transplanted the internal workings of their device into a donor device but this may be firstly a little complex and secondly quite costly, you could source a damaged donor from eBay but the first option is probably best.
Why your screen dims and flickers, honestly I can't say. It could be a faulty screen, which the above could fix. It could be a faulty light sensor. It's hard to say without seeing the severity of this. How bad is it because it could just be the auto brightness kicking in, that's if auto brightness is activated.
Anyway, hope that goes some way to helping. Anymore questions please ask and good luck.
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