I, and I alone take the 4Runner in for service. I go to my dealership because, well they service a lot of 4Runners and that gives me some confidence. That being said, when they roll the vehicle out, I go over everything, including checking fluid levels and my tire pressures (they love to drop them back to 32). Last time I was out there, one of the mechanics saw me doing this, smiled and gave me a head nod. The look on his face said it all.....They do the work, but it's always smart to check things yourself. Mistakes happen, especially in environments where people are working on several projects all at once while not getting paid like they should give a shit. That said, this is not an "oops, our bad" type of mistake. Oil overfill can cause issues like foaming etc, but I have no idea what 2x the amount of oil would do. You need to get this documented with the dealership for future issues. I've run test vehicles with 120 to 130% oil levels that had no issues (they were running 20+ hrs a day), as there will always be some leeway engineered in. However 200% seems like it is out of scope and not something that would be planned for. The good news is that it sounds like you caught it right away so hopefully any damage will be non-extant or very minimal. Good luck with the dealership, sometimes they will do right by their names and sometimes they suck.