Morel MDT-33 soft dome tweeter

It's super easy. 

Just keep in mind the magnet is super strong, so you want to keep good control of your screw driver, and when you pull screws off, keep them far away so they don't jump and break the diaphragm. 
Since you are already thinking of replacing the diaphragm, you shouldn't be too scared to try and repair them. :)

If they just have dimples, you could disassemble them and push them round from inside.

If that's not good enough, another less expensive (than buying whole new tweet) is to call Madisound about replacement diaphragms.

It looks like this is the modern replacement:

https://www.parts-express.com/morel-et-338-1-1-8-soft-dome-tweeter-matched-pair--277-070

First, try Google.

Google will direct you to Parts Express and Madisound. :)

Best,

E