Well it's done.
We made it yesterday and are very proud of the completed product!
What I can say is that the first warning was legit. the mounting for the CPU fan was needed as what was provided was too small. We didn't have time to get the mount sent to us. So I came up with the idea to simply "cut" the female housing ends off and thus make them free to screw into. The solution worked and we got the CPU fan mounted with no problem. It posted without issue once all the PSupply cables were connected and voila!
The PC has two M.2 slots one under a heat sink I didn't see that at first. When he got it home I talked him through on how to dismount the GPU and insert the m.2 under the heat shield. and then the re-assemble of the GPU etc.
Special thanks to those that contributed their ideas, and to Linus and staff that cultivated a love for PC culture and building.