With care you can take these apart. One thing to get right is that when you put it back together don't over tighten the screws. The cover plastic breaks if the screws are more than snug. You can get it to the stage of disassembily shown in the parts fisch. Problems start when riders try to take the speedo or the tach units apart further.
If the gaskets #4, #11 and #16 are in usable shape be careful with them. They are NLA. (a term used for our bike parts that are No Longer Available)
#15 should be available if you need it.
And don't drop or loose the tiny screws they are NLA.