What is the best way to change the transmission fluid and filter?

It is a good idea to service the transmission and filter. Some say don't do it if the transmission is old, but I will tell you want will ruin the transmission that is a clogged fluid filter. Here is a generic guide to help you step by step with instructions in the diagrams below to show you how on your car:

https://www.2carpros.com/articles/how-to-check-and-add-transmission-fluid

Fluid Types
Automatic Transmission Fluid

Ford Part Name

- Motorcraft MERCON LV ATF

Ford Part Number

- XT-10-QLV

Ford Specification

- MERCON LV

NOTE: Automatic transmissions that require MERCON LV should only use MERCON LV fluid. Use of any fluid other than the recommended fluid may cause transmission damage.
Capacities
Automatic Transaxle

6R80 .................... 13.1 quarts (12.4 liters)

Check out the images (below). Let us know if you need anything else.