Reviving RedSea Max 250 - Help with timer replacement

[Markbunga]

Hi all,
Just started reviving my Red Sea max 250. Lots of stuff to replace but so much fun getting back into the hobby.
Had to replace protein skimmer pump and repair a lot of hoses, tubes, etc,

Main issue is replacing the timer which is dead.
Does anyone have any tips or instructions on how to replace?
Thanks for any and all help.
Cheers,
Mark