Just an update: Did my cleaning/op rod replacement Friday (04/13). Tearing it down was quite easy, I had a little trouble figuring out how to separate the follower rod from the spring but it was just pulling it apart. You seem to be right about the operating rod, it was slightly less than 19" and the coils were quite compressed towards the follower rod. I'll attach some photo's of the cleaning, you can see the difference between the old/new.
Also there is a photo of a 'FULTON ARMORY - ARMORY
M1
GARAND GAS CYLINDER WRENCH' (blue thing). I though that was for unscrewing the gas port screw at the end when I purchased it. When it arrived it was quite large and I realized it fits around the end of the gun. I don't really know what it is for, do you? I used a regular Flathead to screw/unscrew the gas cylinder lock screw. I'll probably end up stripping it if I keep doing that, so I'll look for the proper tool at a gun show or purchase one online before my text tear down.
Assembly went fairly easy. Getting the op rod spring in and reattached was a but difficult but I did it. Hopefully I used enough lubricant.