Help me get one good Nexus out of two with issues.

[Unkempt Quigley]

I had a 32 gb Nexus 7 (2012) which was working great, got the issue with the loose charging port, but I had managed to get around it. In the midst of installing kitkat update, it got stuck at 40% and wouldn't power off. I was finally able to power it off and have never been able to get it back on again. It is not recognized by computer, I've done all the button combinations, using the original charger, etc. Anyhow, I got a used 16 gb Nexus 7 (2012) which does power on and the charging port seems ok. However, apart from being less gb, the screen on this one is yellowing around the edges and it seems to drop wifi connection all the time. I did try removing the 100% charged battery from the 16 gb and putting it in the 32 gb, by the way, in case it was a battery thing, but that didn't work to make the 32 gb light up.:'(. What parts would i change in order to get a good Nexus out of the deal? If anyone can point me to youtube links or whatever else, I would greatly appreciate it. Thanks!!