I've only done 1 stack so there will be others that can add more info, but I'll share what I did with mine.
Powdercoated the shelves and bottle rests gray and the front face plate white. Need to talk with your powder coater about coating over the galvanizing on the shelves as the galvanic coating can offgas and cause the powdercoating to bubble. Looks horrible. I ended up putting my shelves in a tub of water with some muratic acid. Gives off toxic fumes, so do it outside, but it eats off all the galvanized coating and the shelves turned out great. Lots of posts on offgasing discussions on the board
Rest of the stack was taken apart and zinc plated. Take pics of everything you send to the plating company so you know that you get all the pieces back. Only piece I did not send in was the bottle gates. They are pot metal and can be damaged by the plating process. Just polished those myself and they cleaned up nice. There used to be a problem reattaching the bottle gate to the gate arm because the shoulder rivet required was no longer made. Now either Funtronics or SodaJerks has them available on their site.
Take lots of pics as it comes apart so it is easier to put back together. I'm sure I left some things out and others may have differing thoughts. Overall, redoing the stack was may favorite and most rewarding part of restoring my machines.
Thanks for the info. I was wondering if it is standard to replace the springs? Also, with the various coatings, did it affect the performance of any moving parts? Since you powder coated the shelves, did you powder coat the inner cabinet to match?