can I replace the instrument cluster with a used one?
Maybe YOU can, but I would need a professional mechanic for a job like that. 
Seriously though, you may have to disclose that the odometer mileage does not match the actual mileage when you sell the car. Other than that, yes, you can replace it with a used one.
That’s actually a legal requirement in the few states I’ve lived in, and in the UK, Holland and Germany. Can’t speak for the rest of the world, nor the rest of the US, but I suspect it does. Having said that, if it’s digital, I’m sure it’s stored somewhere, but I can’t tell you which component it’s stored in. Write down the current mileage, and when you install the new one, write it down again. A note with date change, old and new mileage is what you need. I think most titles have a spot for mileage differences like that when you transfer title.
Changing them out is relatively simply, but be careful when pulling the dash apart to get at it, as there are little clips that will pop and try and hide from you. A #2 philips, a Torx or two (I would take at least a T-10, 25 and 20), and you should be able to get it apart. Maybe some pliers, a crescent (just in case) and a couple long flat screwdrivers (prybars).
Use caution with the wiring in the back. They used to be pretty hardy connections, but they’ve been getting flimsier as time goes on, and many will just plug into the plastic trace sheet on the back of the unit.
Practice how it comes apart in the junkyard. Bring enough tools with you to get it all apart, and pay attention to the clips and screws. In fact, pocket a few extras in case yours don’t come out as they’re designed and either hide or break. That way, when you do yours, you’ve already seen it once.
Chase