Bro those websites (i'm guessing it's Zenith motors) are spouting BS. If you wanna get yr mittens on an el primero you'd be looking at ebay for olde movados and ebels -> anything with the el primero movement aint gonna come cheap. We're talking upwards of 1300K in my experience. Once you do get a hold of said watch, you'd be loath to take it apart for such a project coz those olde watches themselves have such character!
I tried that long and winding road but turned back at the precipice