I hope you guys can provide some help!!

I have a 2001 ml320 w 80k miles on it. There are a couple of items that I need some assistance.

1. Is there a reservoir for the rear windshield wiper fluid? I fill the one under the hood, however nothing comes out of the rear wiper.

2. The three headrest in the rear (2nd row) do no come down...I press the latch, however they wont come down but they will go up. (starting to obstruct my view)

3. Today I noticed/heard that she seems to be idling high when in park or neutral (around 16rpm) I don't recall it ever doing that before.

Please any assistance would be greatly appreciated