This is as complex procedure. I suggest you buy a repair manual if it is not obvious to you, and you don't have experience.
Conventional drum brakes.
You don't, you replace or rebuild the engine.
How do you change the thermostat in 1999 Mercury Villager
Yes.
Probably around $200 for the tank, and $200 for labor.
According to the 1999 Mercury Villager Owner Guide : ( 20.0 US. gallons )
In the engine.
No, no room.
134-A
Brakes come in two types: disc or drum.See "Related Questions" below for coverage of both types...
4.5 quart
ABS was an option. Not all have it.