Card arrived last night. Fitted it after work today. Went OK 👍!
remove 'lid' of laptop case
Remove CD/DVD drive (wasn't expecting that, but it was easy enough)
Remove a panel sitting above the card (wasn't expecting that, took a while to figure out how, but then it was easy enough)
Swap the card
PC is still working - writing this post on it.
Just opened the DAW and played a track with typical number of tracks, plug-ins etc. Yes, it's got the 16gb and plenty of headroom.
Thanks everybody!