Removal is fairly straightforward. Get yerself a piece of pipe a bit longer than the steering shaft and slightly larger in diameter such that the shaft fits - but allows the worm to catch up on the upper end.
Put the shaft down the tube with the worm end up. And then stoutly "rap" the pipe on a concrete surface. The impact and inertia of the shaft will pull the shaft from the worm. You might do well to stuff a rag into the excess pipe so the shaft doesn't rebound within the pipe when it comes loose or get damaged on it's thread as it itself hits the concrete. Maybe put the nut on it to protect the thread?
One of those "knockoff rear hub removers" is the same thread as the steering shaft and can be used to protect the threads of the steering shaft very nicely.
Now getting the worm back on will be your next challenge. One dodge on this work is to thread the INTERIOR of the worm end of the steering shaft and use a bolt/allthread and nuts to "pull" the worm back onto the shaft. After removal of the bolt/allthread and placement of the shaft/worm back in the steering box, nobody will be the wiser. The use of this techique and others are discussed in the forum.
Oh - before removing your worm - MEASURE carefully the distance between the worm and the threaded end of the steering shaft. You need to duplicate this length EXACTLY or you'll run into troubles re-fitting everything back together.
Vince Falter at Fordgarage.com has a chart showing the dimensions - but better is to duplicate what you have. Of interest is the top three lines of the chart at
http://www.fordgarage.com/pages/steeringshaftwormchart.htm
Good luck. Removal of the worm is pure physics at work.
"An object in motion tends to stay in motion."
Joe K