Ignition switch
The electric Ignition Starter Switch is from the 1988 to 93 Pontiac Lemans (USA). AIRTEX / WELLS Part # 1S6210 {#4971498, 7848744, LS589} on rockauto.com. BWD Ignition Starter Switch Part No. CS302 at Advance Auto Parts. Key cylinder should be from the same model but not confirmed.
The electrical part is held in by a set screw on the steering wheel side and a pin on the front side. You can remove without taking the steering wheel off by bending the end of a small screw driver to a right angle and using this to remove set screw. The pin is suppose to stay in but if it was overdriven you will have to remove it to get the part out. The pin should be flush with the housing and will be recessed if overdriven. The overdriven pin will come out if you press it in with a small screw driver or punch and pull hard on the switch. You might break the part removing so don't do this unless you plan on replacing. If you have to remove the pin drive it back in until it is flush before replacing the switch. This switch is inexpensive (less than $20) and should be replaced if you're having any problems such as the radio not staying on. You can disassemble and clean contacts as a temporary fix but should plan on replacing if there is any pitting of contacts.
For key cylinder removal, see LEC write up.