transmission problem?

I'm new to posting and new to my 2000 ford excursion diesel. I had a 2000 V10 Excursion and traded for a diesel. I've been having it worked on and trying to get it to run like it should, based on my research of mpg, turbo, towing, etc... Thought it was doing OK. Then this week, a friend is driving it and it loses all gears instantly. Now it's sitting in my driveway motionless. There's no reverse and there was no slipping to indicate transmission problems leading up to it. When we went to check the transmission fluid after towing it home, the dip stick tube had broken off. But, we didn't see any fluid on the engine or ground. Also, the gear shift moves through the gears but doesn't engage at all. I'm a little puzzled that it happened so fast. Any ideas, or places to start looking, I'd appreciate it.

Late reply, but here is where I'd start for anyone with the same symptom: with the dipstick tube broken off, assume the fluid is low or gone. An automatic that suddenly loses every gear, reverse included, very often just can't pick up fluid, and it looks exactly like a dead transmission.

Seal or replace the tube, add fluid until it shows on the stick, and check it with the engine running, in Park, warm. If it drives again, find where it went (the broken tube is a good bet, also check the cooler lines) and look at the fluid: dark and burnt smelling means it may have been damaged running low.

If it is full and still won't move, look at the shift linkage next: whatever broke the dipstick tube may have knocked the shift cable off the lever on the side of the transmission, and then the selector moves but the transmission never leaves Park or Neutral. Only after those two would I suspect internal failure.

Dana