I've done this. It's a pain in the arse too. Especially when you have to guess your way through it.
This is what you need to do, really.
1. Go through all the procedures to separate the main body from the legs.
2. There's the plastic thing on the "floor" of the drone body, held in place with four screws. Those need to be removed.
3. Remove the sides on the main control unit.
4. Remove the video cable plastic cover under the main control unit casing by it's 2 screws.
5. There are two cables there. One on top is wrapped in foil and is smaller. That is for the rear vision system, be careful with it. It's held in place with two drops of glue on either side.
6. Peel up plastic floor covering so you can see where the cables are going now.
7. Disconnect rear vision system cable. Beneath that is the gimbal video cable, it looks like a bunch of tiny wires going unprotected into the plug, it is also held in place with 2 dots of glue. Detatch that one and move the vision cable out of the way. I usually use a bit of masking tape for it.
8. On the other side now you will find the power cable for the gimbal. It's the one that's closer to the "back" of the drone. Note the locations of other cables in the bottom of the drone body. Those will have to be replaced to make it all fit together.
9. Now pull the cable grommets out underneath and the whole assembly should come out once you pull out the gimbal dampeners from the body and forward vision system.
10. Now reverse the process to install the new board.
11. ???
12. Profit
All told, the repair should take an hour or so. Be slow and careful. Any slips of a screwdriver could break something off a board or rip a cable.
Also, there's a little plastic thingy for the led light next to the selector switch for computer/phone paring. Be sure not to lose that.
