My wife's 1996 A6 quattro wagon is running ice cold. I'm suspecting a bad thermostat and would like to cahnge it this weeknd. Where is it located on the engine and is changing it a big problem? I've yet to buy the service manuals. I'm sure that would make it easier. In the meantime a quick walkthrough would be appreciated. Is there a special coolant I should be using thats not green?Thanks,