2 cans should be enough. The actual amount should be on a sticker on the A/C housing.
R134
134-a
134-A
Through the low side A/C port.
The amount of refrigerant required for an air conditioner is always on a sticker on the unit or nearby.
It should be the same.
According to the 1998 Mercury Villager Owner Guide ( 5W-30 ) is the preferred oil
The Villager has an electric fan and does not use a "fan belt".
R134a
10w30
1994 Mercury villagers come factory charged with R134a refrigerant. Vehicles built 1993 or prior were charged with R12 for note.
The 3.0 litre V6 engine in a 1998 Mercury Villager has a timing BELT