Mega Mileage from Your Super Lexmark IBM Model M Mechanical Keyboards

It's worth keeping the old boards and the board parts. Also be mindful that there are 103 and 104 Keyboards, small and wide space bars, and different models of boards.
Some things will be mostly interchangable, and somethings are not. I have never bought the 122 key boards.. So I no experience of them.
Keeping them clean and keeping the dust out of them is a good idea. They last a lot longer then. Also avoid picking them up and holding them upside down - it stops the dust and grit and grime from going under the caps and then into the slides and key switches.