Note that there are two hardware versions of the replacement part. One has one antenna connector, the other has two antenna connectors. The iFixit part labeled "Sprint" is the one-connector version. It is the most common. It may be labeled "16GB" on ebay and from other sellers. My 32GB T-Mo device required the "16GB" version of the hardware, so use caution when ordering. The iFixit part labeled "Verizon" is the two-connector version. You may see this one labaled "32GB" on ebay. My understanding is that the 2-connector part is for Verizon & AT&T Windows M8s, but I could be mistaken.
If you don't know which hardware you need, and you are ordering parts before cracking open your device, I would suggest (at least at 2017 ebay prices) ordering one of each and returning the one you don't need.
The two cables at the top of the motherboard near the camera, mentioned by commenters above, will have a small rubber pad on top of them. You may wish to keep that pad. Also not pictured here is the LED surround. It can easily come loose from the motherboard. Don't lose that either.
There is a small rubber pad stuck to the inside end of the headphone jack. You can see it in the 3d picture that goes with this step, slightly offset to the right. Your new part will almost certainly not include this rubber pad. Stick it on the new headphone jack. This helps keep your M8 a little more water-resistant, as the pad is covering a small hole.