If you mean the oil pressure sender it's right next to the oil filter.
According to one of Fords websites : The 1998 Mercury Villager uses the ( Motorcraft RS-519 radiator cap ) It is a ( 13 PSI cap )
on my 1999 ford mercury villager its on top of transmission under the van
In a 1998 Mercury Villager, the mass air flow sensor is located in the air intake tube. The air intake tube goes from the air box to the intake.
It should be the same.
O2 sensors are always located on the exhaust system.
All major relays are in the relay box under the hood.
According to the 1998 Mercury Villager Owner Guide ( 5W-30 ) is the preferred oil
10w30
The 3.0 litre V6 engine in a 1998 Mercury Villager has a timing BELT
In the dashboard behind the small grill to the right of the steering column.
Top rear of engine directly under the air intake tube/throttle body.
R134