Vehicle speed sensor question

I've been reading the posts on vss's. I've got a 98 Windstar with basically the same problem. The ABS lite won't go off after the initial 25 mph increment.
I've heard the vss is in a rather difficult place to get at. I've seen some hints on how to make it easier to replace.
How can a person check to see if any one of the magnetic pickups are bad? What test can a person do, relatively easily ,to show the condition of the four pickups?
I'd like to see if perhaps a pickup is bad and maybe I can replace that instead of the vss.
Thanks in advance.

Please post details about your "problem". . .

Karl

The ABS light starts out not lit. I start the vehicle and begin driving. After a short while (less than 1/4 mile) the ABS light comes on.
I am believing the problem to be a wheel speed sensor. Or, perhaps one of the magnetic pickups at each of the four wheels. Or, perhpas more than one pickup.
I was wondering what procedure would be used to check the pickups.

To avoid confusion....
VSS (Vehicle Speed Sensor) is on the transmission....

Wheel sensors are at each wheel of the vehicle.
You can see them in my pictures of my brake jobs
http://community.webshots.com/album/201931518cScpNK
Spraying them off with brake cleaner, if they are dirty with brake dust, etc might help.
Some have posted that the rear sensor can be a bit far from the "gear" and have adjusted it to be slightly closer.
You might give the front ones a good look for a loose / hanging wire that may have been caught and damaged.

Thanks for your replies.
I understand that the VSS is up under the exhaust manifold. I also understand that it's not in a real convenient place. So, I'd like to insure that the wheel sensors are not the problem before I try getting at the VSS. So, I'm wondering if there's a simple quick way of checking the output from the wheel sensors to make sure that one or more of them are not bad.
I have blown the front ones off with air and thus cleaning them. But, that hasn't helped.