Another note as a follow up: After the replacement all seemed fine, though i noticed start up was really slow and it generally didn’t feel as responsive as before the swap. Getting worried about the replacement board (the ZIF connection of the trackpad was missing on the ‘new’ board) i ended up resetting the NVRAM. This miraculously solved the problem for me.
And as the new board has a different serial number, this should be updated for iCloud…i guess, as this is the serial that appears in ‘About This Mac’.
This guide was essential in repalcing the logic board i’d bought off ifixit. Great, a new lease of life for my macbook air. Phew …