Dell XPS 14 L421X - Help and Guidance needed re some repairs/upgrades

I have been fortunate to have been given a Dell XPS 14 (L421X) by my son. Unfortunately it had developed a keyboard fault whilst he was working abroad and even though it was under warranty they were only able to source a local keyboard they weren't able to get the UK one which was needed.

Moving forwards I intend to do 3 things,
1) replace the keyboard (this has already been sourced from an official Dell reseller),
2) increase Memory to 8 Gb (this has been received direct from Dell) and
3) replace the HDD with a similar sized SSD (500 Gb) Samsung 850 EVO or Pro, removing the m-SATA drive at the same time.

I would just like to know the correct order in which to do these upgrades/repair. My assumption is that I need to:
1) Create a Boot DVD as I want to reset it to factory defaults then all his stuff is cleared off (I have an external DVD writer already).
2) I would then open up the laptop and replace the keyboard. Sounds simple I know but having downloaded a copy of the owner's manual and I can't say I'm looking forward to it.
3) At this stage I would replace the HDD and remove the mSATA SSD as it is now surplus to requirements. Are there any settings that need changing in BIOS as a result ?? Also what is the best BIOS to run as remember seeing something somewhere about the latest BIOS mucking about with SATA III ??

Once everything is back up and running I may well then upgrade to Windows 10 as Windows 8 is the default on the Laptop and I don't really want that.

Has anyone got any experience of what I am trying to achieve or suggestions ? All help very greatly appreciated.