They're not password-protected. You can rename the .MU file that you saved to an .MC file and it should just work (as you said above).
If you want to re-name the file to another name, you just need to update the .CAM file with the new name and as long as no subsequent mission reference the new mission incorrectly (since you changed it), then it should work fine.
P.S. I'd be AMAZED in Mission3 ("Missile Test") would work in DW without some serious tweaking. That mission was so "delicate" that if the wind blew the wrong way the Udaloy (or was it a Sovr.?) wouldn't fire at the airbus. With the scripting in DW, that mission would have been SO much easier to create... Actually that mission is probably the reason WHY we added Scripting in the first place...
