I put together a Raspberry Pi 3 with a 7″ screen. I am running Retropie on it. I built this to try out homebrews and fan translated games.
Just to warn you guys, there is a hardware issue with the screen, it is upside down. All that means is that the power and HDMI sit at the bottom and it will fall over. You can not flip it around.
So In Terminal, type “sudo nano /boot/config.txt”
Add the line “lcd_rotate=2” to the top of the file.
Here are the parts I used from Amazon