The process is relatively straightforward if you have some experience building your own system; I strongly advise to follow the instructions step by step carefully.
Some difficulties I encountered:
The pigtails might be difficult to disconnect - take your time and don’t just yank them. Otherwise you might have to repair a connector
Some of the holes in the chassis might not be a perfect fit - in my case the 2 and 4th holes have a straight notch to hold the antenna connectors in place… but the connectors did not so I have to widen the holes a bit
Each of your installations is unique. In my case, I went for a full factory reset after installing the upgrade package. But in my case I have installed an internal SSD.
In any case, things seem to be working as normal. Below are some photos.
Open the router
Install a connect new card