There is no definitive guide yet but if you pretty much follow the teardown to step 9 skipping 7&8 you should in theory be able to swap the drive out but do note that because most of the case is clipped onto the metal frame that you may not be able to put it back together If you brake the clip tabes (and you will void the warranty) so "enter at your own risk" kinda deal.
Also something i have notice is if you put all your games on an external drive it helps a lot as the only thing accessing the internal drive is the os and with all the game external loading is faster as it has no os tasks I.E. the xbox can read from both drives at the same time for there designated taskes
EXAMPLE: fallout 4 used to be installed on my internal drive before i got my external, the load times were about 1-2 min. And loading things like the guide toke forever to load but after i got the external the game loads a lot faster about 20-80 sec. and the guide loads almost instantly hope i could help