For those of you who have done this a few times, you may have found a
way that works for you. For those of you who have yet to replace this
switch - this may save you a little blood, sweat and tears.

Tools:
Flat-tip screwdriver, standard length
Flat-tip screw driver insert tip (hex shaped, about an inch long,
commonly found on ratchet screw drivers where you can use many types of
tips interchangeably)
Phillips screwdriver
Telescoping antenna magnet (commonly used to pick up dropped metal
parts) I HIGHLY urge you to have this!
Large ice chest or long flat bench to lay on.
Padding for the bench like a blanket or foam padding.
Pillow or padding as a head rest
Flashlight

Disconnect the negative battery cable.

1-) Remove the plastic cover beneath the dash, over the brake and
accelerator; note the white plastic slides this mounts in.

2-) Unscrew the radio amplifier unit and set aside (don't unwire it,
just move it aside to gain clearance.

3-) Place a large ice chest (cooler), or picnic table bench at an
angle, butted against the open, driver side door jamb. This will be a
"table" for you to lay on instead of sitting in the seat, or having to
lay on your back on the car floor. To access this switch you need to be
on your back facing upwards and comfortable.

I used a foam egg-crate from my bed, laid on top of an ice chest, with
a pillow on the driver's side floor. Once I was positioned correctly
and comfortable, I could do the job patiently and carefully.

4-)  Using only the flat-head insert (about 1 inch long), unscrew the
lower screw (left side) on the switch with your fingers.

5-) Using a flashlight to see, unscrew the upper screw with a standard
screwdriver. Remove the switch.

Installing a new switch:

6-) Place the new switch on the ignition - it can only slide on one
way.

7-) Insert the lower screw and snug it with the hand-held flat-tip
insert using your hand only.

8-) Using the telescoping antenna magnet tool, put the upper screw on
the magnet and use the magnet tool to insert the upper screw in its
hole and gently turn it as many times as you can. Carefully use a
standard flat-tip screwdriver to snug it into place.

9-) Sit in the driver's seat and with the left hand hold the switch
into place while turning the ignition key back and forth with the right
hand. This is to firmly seat the switch. Don't let go of the switch.
Holding the switch, lay back into position and tighten both screws.

10-) Reinstall the radio amplifier

11-) Reinstall the plastic cover, noting the slide mounts.

12-) Reconnect the negative battery cable

The key things here are the magnet, the small flat-tip insert, and the
flat bench to lay on comfortably.

Good luck!