the only thing you can upgrade on the xbox itself is the hard drive, you can upgrade the hard drive to an SSD to make boot up times and game load times much faster. also you cannot put the hard drive from the xbox into your PC, because it wont start.
on the part where the joycon slides on, there is a button, if you press the button on both joycons, then slide them on for about 7 seconds, then slide them back off, press the button on the joycons again, and they should sync up.
the same thing happened to me while installing high sierra on my 2010 macbook pro, the slowness and high fan speed is indicating that one of the temperature sensors inside you macbook air have gone bad and is reading an incorrect temperature. this makes the system thermal throttle, which makes the fans go full speed, and makes the kernel task go high. if you leave the high sierra installer on for about 2-3 days it will finally finish. once it finishes, you can either install macs fan control, and see which sensor is bad and replace it. or you can delete the MacBookAir6,1 file which will completely disable the kernel task but you will have to use macs fan control to slow the fan down to speed. here is a tutorial on how to delete the MacBoookAir6,1 file