[OldenburgerM3]

Just did this too. Easy stuff. My differential on the OEM fluid started making occasional brrrp noise on right turns, possibly only when cold. Anyway I am on RedLine from ECS now, for LimitedSlip Differentials. If I encounter any problems I'll post.
I also noticed that a good bit of fluid came out of the fill port initially, so before I plugged the fill bolt I shot a pump-load of fluid in and closed it. Let's hope it's not too much but I doubt it. My car's relatively level: ramps and stands.
Had to get a 14mm Allen but Amazon had it (not Sears, not Ace, not HomeDepot).
Edit to add: after several weeks of evaluating, the brrrrp noise is gone from the parking lot turns.