Private. And yeah, that's a realistic cost. Remember the engine bay? GM was looking at 5hrs work just for a spark plug swap. You have to drop the motor just to get at anything. It's $800 just to change the intake gaskets. The $2000 estimate includes $300 a piece for replacement heads. That may not be needed, but with 200K on the clock, there's a good chance (according to the mechanic) that the antifreeze may have corroded the heads more than can be safely machined flat. But (also according to the mechanic) there's little else that goes wrong with these motors. All the trouble stems from the intake. The bottom end is rock solid and once this job's done, it should be good for another 200k.
This is a shop I trust. And the price estimates are straight off an identical job they did last week. Same year van, with similar milage. That one needed the heads. The truth is that it's 80% that it's only the intake manifold, and that the $800 repair would solve it. But there's no way to tell if the heads aren't also leaking without going in. There's no test to separate the two.