The Haynes manual will not help you one little bit with this job I'm afraid.
Incidentally, neither will the Ford TIS DVD.

Here is a "how-to" based partly on what I have posted in the past:

I would advise getting a new retaining pin before you start as the chances
are you will destroy the old pin during removal. It is not supplied with
the new sensor.

Using a pair of pliers, bend the flat clip out of the way. (It does not go
in to the hole; it just presses on the casting.) It will probably detach
itself when you do this. Grip the pin with a pair of side-cutters close to
the transmission housing and then use the side-cutters to lever the pin
out. You will have to keep repositioning the side-cutters along the length
of the pin as it gradually moves.

Others have suggested clamping mole grips on the pin, then tapping the mole
grips with a hammer. I tried that, but it didn't work for me. YMMV.

Once the pin is removed, the VSS is still a bit hard to get out. It has two
O-rings on it that make it a tight fit in the housing. DO NOT be tempted to
try to knock it upwards with a drift and hammer. This might result in the
sensor breaking, leaving half of it in the hole!

In the limited space available, wrap a piece of rag around the sensor and
rock it GENTLY from side to side and twist it as you pull upwards. Take
your time and it will eventually come out.

I have seen it suggested that removing the transmission fluid level plug
before you start makes sensor removal easier. I assume this is to prevent
the vacuum created by pulling the sensor out tending to hold it in place.
I'm not sure it would make any difference, but I suppose it would give you
the chance to check the fluid level whilst you are under the vehicle.

I agonised for ages before tackling mine, but once I took the plunge I did
it in less than 20 minutes.

I hope this helps you. Let the group know how you get on.

Chris.