The Villager PCM is located far under the dash, near the firewall. It requires a fair amount of disassembly to reach it, so I'd suggest actually making sure there is something wrong with it before attempting it.
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 )
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.
In the engine.
134-A
No, no room.
on my 1999 ford mercury villager its on top of transmission under the van
ABS was an option. Not all have it.
4.5 quart