Here are the basic instructions for taking apart the hub and replacing the main board. 

Tools required:
Phillips head Screw driver ( plus shape + )
Camera ( Helpful for tracking your progress and reassembly )
A couple of small trays or bowls ( sorting screws )
Needle Nose pliers ( always helpful for small electronics projects ;)

Remove the dome, food pod and food tray.  
If you need more information on that you can refer to the "Dissembling the hub" guide here. https://app.intercom.io/a/apps/swragh2u/articles/articles/104414/show

Remove 4 screws around the electronics casing
The one screw in the center near the food tray (Orange circle) 1 is unique to these 4, just remember where that goes, take a photo if you need, and separate it in a bowl.

Remove 2 screws on either side of the Mainboard
After you remove the electronics housing you should see the green mainboard sticking up with a number of wires coming from it, with 2 screws on each side. Take them out and set them aside in a separate place from the other screws.   

Next unplug all the wires from the mainboard
But before you do, take a photo of where they are all plugged in and coming from. This will be your guide to plugging in your new board.  Also it's important to try and grab the plastic clip and pull it out from the plug instead of the wires.  Pulling on the wires risks causing a loose connection or pulling a wire from a plug, and that's a lot more work than pulling on the plugs.  You may prefer a set of needle nose pliers to do this.

Unplugging the wires with needle nose pliers.

Next plug in the new mainboard
You may have an unused port, but positioning should all be the same between both boards.

If you have a new photon chip that plugs into your new board you can do that now.
Make sure to push the chip in on the sides where the soldered pins are.  You do not want to push on the center of the chip, you can risk damaging the chip if you do so.  Also double check all the pins are in place and none are hanging out.  The small micro USB slot should be pointing to the side of the mainboard and NOT the center.

Reassembly time!  Now putting it all back together.  
But wait! Before you do that, you may want to plug the power in and test that the food pod motor, touch sensors, food tray, dome switch, all work when triggered.  This way you will know everything is wired up correctly and you can proceed to re-assembling the hub.  To test, just plug in the power, put the food tray back in, and hold down the dome switch in the back.  It's a metal flap in a socket, your needle nose pliers might come in handy here, or a small knife or stick of some sort.
Link with dome switch location.
https://app.intercom.io/a/apps/swragh2u/articles/articles/1054211/show

When you do this, you should see the food tray move, then the food pod motor spin, and then just touch the touch sensors, the system should make a different sound for each touchpad.

Screw in the 2 screws on either side of the mainboard.
Refer to your photos to be sure you are putting them in the right spot

Place the electronics housing back on.  
Be gentle when placing this part back on, it should go on easily, and is perfectly sized to fit everything without stress.   Don't pinch any wires.  If you find yourself forcing anything, step back, re-align and place it down again.

Replace the electronics Housing Screws
Once the electronics housing is down and lined up with the 4 screw holes you can put your 3 screws around the outside back in and the center screw in.

Tada! Your an electronics assembly technician now!