So if your driving through the a not so nice part of town at 6am in the dark, and you notice your headlights are awful dim, your turn signals aren't working and your 4 miles from work.  Do you:

A.  Pull over with no flashers on the side of the road in the dark in the worst part of town.

B.  Finish driving to work with almost no lights and no signals

??

That little issue aside, your alternators not working.  Replacing an alternator in a 2000 Ford Windstar is an easy job.

1. Disconnect Battery cable.
2. Jack up Front Right of car (use jack stands for safety).
3. Remove Front Passenger Tire
4. Get another set of hands
5. Reach up in the passenger Tire well and locate the Tensioner pulley
6. Use a 13 mm wrench and remove tension off of the serpentine belt
7. Using your other set of hands (remember your under the car !), take the belt off of the alternator
8. Disconnect electrical from alternator (one snaps in, one bolts, the ground is on the mounting bolt).
9. Remove Mounting bolts
10. Take to FLAPS (Friendly Local Auto Parts Store) and buy a new / rebuilt alternator (take the old one with you or you'll have to pay a core deposit).
11. Mount Alternator
12. Reconnect Electrical
13. Crawl underneath Car and pull on 13mm wrench to give slack for Serpentine belt
14. Using your other set of hands put the belt back on the alternator
15. Put Tire back on, lower car
16. Reconnect Battery
17. Done - Easy, takes about 30-40 minutes.

This is a good time to relace your belt and possibly your idler pulley if you need it; i had done that about 30K miles ago, so it was ready to go:

Some Pictures of the work:

This is the bad alternator, you can remove it and have them test it, but one way i've always found to test one is keep it in the car, with the car running touch a screw-driver to the back, if it's magnetized than the alternator is working, if it isn't, it's toast.

This is the inside tire well where you need to reach up and put a 13 mm wrench on the tensioner pulley, it's tight but not difficult.

You can just see the wrench hanging off of the tensioner pulley.