I have a2002 Ford Explorer, and the transmission has been slipping a little bit. Will having the transmission flushed and refilled do any damage to any internal parts of the transmission?

consult the book (Chilton's/Haynes)or call your local dealer service dept, But most sealed systems have an over flow or fill level plug under the pan. Be sure it's the overflow and not the drain. I've never heard of a flush hurting a trans but anything is possible.

The sealed transmission in your vehicle requires a special tool to remove the plug on the pan. A replacement plug can be purchased and will be used to fill the tranny via a pump. The fluid must be heated before being pumped in and excess drains out via the tool. When it stops dripping out the system is full.