From WikiAnswers for a 1997 model - -
You will need the following tools:Steering wheel
Torx bits (get a set, you need 3 sizes)
Inverted Torx ( a set is
available at Schucks/Kragen/Checker Screwdriver
A few zip ties
DISCONNECT THE BATTERY
Start by disconnecting the yellow wire under the dash for the airbag. Now turn the steering wheel
90 degrees to access the underside of the steering wheel. You will have
to insert a smaller size flat blade screw driver into the 4 holes on
the back of the steering wheel and rotate them to release the airbag.
Now remove the nut holding the steering wheel on and remove the steering
wheel. BE VERY CAREFUL WITH THE AIRBAG MODULE!! Now remove the lower
column cover with 2 Torx screws. You will now have access to 2 inverted
Torx screws that hold the top column cover in place. Remove the
hold-down ring that holds the cover to the shaft. Look on the top of the
ignition cylinder housing and find the small hole. Insert a small Allen
wrench into the hole and turn the key to "run" position and the
ignition cylinder will come out, now the top cover will come off, giving
access to the ignition switch. You will need the smallest inverted Torx
bit for the 2 screws that hold the ignition switch in. You will have to
cut a couple of zip ties to free the wiring. Now get a Torx bit and a
7mm socket and remove the lower dash panels to get access to the wiring
harness. You will need the 7mm to unscrew a bolt that holds the
connector together under the dash. Just follow the wiring to see what I
mean. Once the connector is loose, you will see two plastic strips that
run along side the connector. These are easy to remove and slide off,
and are keyed so you cannot reinstall them wrong. Hope this helps.
Great answer/directions listed above. I would add that one can use a 3/16" section of brake
line to get the two e3 or e4 external torx screws out (holds the
ignition switch on) instead of buying the whole kit. Buy a 6" or 8"
section of brake line, cut in half, take the cut end and "lightly tap"
it on (with a small hammer) the torx head. The metal brake line is soft
enough to form around the head. Take a pliers and spin off........they
are not that tight nor hard to get off. Otherwise you need to buy the
whole smaller external torx kit (2") and most places don't carry them..
as above I just did the job also and in fact used his answer.
Read more: http://wiki.answers.com/Q/How_do_you_replace_the_ignition_switch_on_a_1997_Chevy_S-10_Blazer#ixzz1zDg1cc9p