Having done numerous machines ranging from straight swaps to complete playfield strip and restores, I can say it mostly depends on the machine.

AFM no problems, whereas something like TZ is more involved particularly if you want to do it properly by cleaning the wiring loom and assemblies and not just hot swapping the parts from one playfield to another.

Essential tool - a decent collection of music to listen to as the monotony of the task compounded with silence will otherwise drive you round the twist!