The most important points are to drop and clean the pan, change the filter, and refill with full-synthetic ATF. Mercon V is a partial synthetic (80 to 85% conventional oil.) Many quick-change outfits will connect a T-Tech machine to change the fluid, without dropping/cleaning the pan and replacing the filter. This is courting disaster. The T-Tech machine will stir up all of the crud in the pan and possibly clog the filter. Two weeks later you may experience catastrophic transmission failure. This is how a Mercury dealer near me gets a lot of transmission business from people who got their transmission serviced at quick-change outfits.
Here are the steps, if you want to do a partial change (this is how most dealers will do it):
1. Obtain proper transmission fluid and filter for your vehicle (some vehicles don't have filters). I recommend you use a full-synthetic ATF (e.g. Mobil 1 Synthetic Multi-Vehicle ATF or Amsoil Synthetic Universal ATF), provided it meets the manufacturer's specifications for your vehicle. Transmissions run cooler (because of the higher coefficient of heat), perform better, last longer, and get better gas mileage with synthetic ATF. This is cheap insurance for protecting the most complex and problematic part of your car. Do it to save money, in the long run, and protect yourself from the big unexpected transmission repair bill. Synthetic ATF offers a "margin of safety" we all need.
2. Transmission fluid should be at normal operating temperature, before draining.
3. Turn engine off and position drain pan under transmission pan and drain fluid by loosening pan bolts. Loosen one corner more than others to direct flow into drain pan.
4. Remove all transmission pan bolts and lower pan carefully.
5. Remove old filter. Some filters are held in place by a bolt or two; however, some are held by a clip. Ensure filter O-rings or seals are removed with the filter. It may be necessary, on some vehicles, to pry out the old filter seal from the transmission housing, being careful not to nick or gouge the seal mating surface. If you find what appears to be a child's toy top, discard it. It's a filler tube plug used to keep contamination out of the transmission during assembly. When the dip stick is inserted, at the factory, the plug is dislodged and remains on the bottom of the transmission pan. It is an indication the transmission fluid and filter have never been changed.
6. Install new filter using the same bolts or clips. Use new O-ring or seal supplied with the filter.
7. Inspect pan carefully before cleaning. Small amounts of fine gray clutch dust are normal; however, if you find metal shavings, there could be transmission damage or mechanical problems.
8. Clean transmission pan thoroughly with solvent (e.g. brake cleaner) and wipe dry, so there is no harmful residue. If there's a magnet, it should be cleaned and replaced in the same position in the pan. Clean transmission and transmission pan mating surfaces of all gasket material, being careful not to damage the surfaces. If the transmission didn't come with a drain plug, I recommend installing a B&M Transmission Drain Plug in the pan at this time. It makes subsequent changes a snap. Carefully choose a location for drilling a 1/2" hole for the plug. Some manufacturers emboss a "0" where the hole should be drilled. Install drain plug, nylon washer, nut, and torque to 20 ft.-lbs.
9. Position gasket on the pan. Some gaskets have four slightly smaller holes, to allow four bolts to hold the gasket in place.
10. Hand-tighten transmission bolts in a crisscross pattern until snug. Use a torque wrench to tighten bolts to proper torque.
11. Refill transmission through the dipstick, using the amount shown as "refill capacity" in the owner's manual.
12. With vehicle on level ground, recheck the fluid level, using procedures outlined in the owner's manual. This frequently involves starting the engine and pausing several seconds in each gear, as the gear selector is run through the complete gear range (PRNDL). Check the transmission and lines for leaks. The final fluid level check is usually made after transmission reaches normal operating temperature, engine is running, and transmission is in Park. This approach may only change 4.4 quarts, or less, of ATF in your Villager.