Get a paper clip and bend it so it's straight. Look at the ignition cylinder where you put the key. There is a small pinhole in the ignition cylinder next to the key slot. Insert the key and insert the paperclip into the pinhole and then turn the key to the left onto the accessory side. The cylinder will pull right out. Then turn the chrome outer ring on the switch to the left(counterclockwise) and unscrew it, then the ignition switch will be removeable from the backside of the dash, pull it down below the dash and disconnect the plug from the old switch and replace with the new switch, reassemble in reverse order, remove the paper clip and you're done. Kenny.
What if you do not have the key?
If you do not have the key then you'll have to drill out the center of the ignition cylinder with a sharp drill bit, preferably a titanium or cobalt bit that will drill thru metal. Use a slow speed electric or pneumatic (air) drill. A 1/4 inch drill bit should do the job. Tedious but effective. I see no other way without the key or call a locksmith at approx. $125.00 an hour. A good $5-$10 drill bit is a lot cheaper. Drill until you see the lock cylinder tumblers start coming apart. It shouldn't take too long with a good brand new sharp drill bit. Good Luck. Kenny/MrBlueOval