You can get the manual here at PartShop! They need our support to keep the site running! They are made by Mercedes-Benz.
As for the rear headrest, have you tried switch on the dash? I think the car must be running to do this. (correct me if the 190s had no dash switch for this)
Engine temp is supposed to run high in traffic, this is normal. But if it gets close to 120, then I'd definitly have them change the thermostat and the coolant (only with MB coolant!!). See what happens after that. I would also suggest WATER WETTER, which can be purchased here too. I haven't used it yet, I actually just bought it and am waiting it's arrival. But other members swear by it's cooling abilities. Also, make sure that fans start at 100C, according to coolant temp gauge.
What do you mean by the car pings when going uphill? The engine, suspension, what?
And welcome to the best MB site on the web!! Congratulations on your purchase! You have a great car. How many miles are on it?
2006 E350 w/ 155k miles (Daily Driver)
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)