You would need to be more specific with your question. You are not providing enough information to supply a meaningful answer.
Screwed into the engine. Follow the spark plug wires.
There is no such part on a Mercury Villager.
yes!
Yes, it should fit.
Buy a manual.
No, there is no "adjustment".
134-a
4.2 quarts
walmart
Powertrain Control Module
1995 Mercury Truck Villager Van 3.0L EFI SOHC 6cylThe Spark Plug Gap.032 (In thousandths of an inch)
Probably about $150 and up.