Easier than I thought, once you have the right tools. Case back was damn hard to get off. Don't even think for a second that one of those rubber opening balls will do it. At a minimum you need proper case wrench AND a case opening vise to hold it onto the watch, at least for the first time you open it.
It was running about -2 to -3/day since I got it. After about a week of trial and error, I'm at +0.15/day for the last couple of days. I think I'm gonna stop now. Capsule is still the same shade of light light blue that it started out at. No worries about Argon, since it wasn't an Ar filled watch, but I'm seriously considering opening it up once more in an Argon filled bag and then resealing it.
Not too shabby. Yes, I know it was running inside COSC spec already, but I prefer slightly + per day over -, since it makes it easier to hack the watch back to sync.