I a fairly certain, both from looking at the images included in the guide and from examining the way that the circle pad is set up on my 3DS, that you only need to remove the cover, back housing and backing of the circle pad to be able to replace the circle pad cap. As far as I can tell, there is nothing that prevents you from removing the cap with the motherboard still screwed into the upper housing.

I have a Surface Pro 6, and it identifies the SSD as a Samsung-made one. This is how it is identified in the Task Manager:

Disk 0 (C:)

            SAMSUNG KUS020203M-B000

            Capacity:         119 GB

            Formatted:      119 GB

            System disk:    Yes

            Page file:         Yes

            Type:   SSD

            Read speed      8.2 KB/s

            Write speed     4.1 KB/s

            Active time     1%

            Average response time           4.5 ms