How do I change a backup light switch on a 1994 Cheverolet 1/2 ton pickup?

I need to know the location of the switch and what it looks like. Where can I get this info online.How do I change a backup light switch on a 1994 Cheverolet 1/2 ton pickup?Square connecter on the side of the transmission. Usually has 4 prongs in it. You can go to Chilton DIY.com, and for $25.00 a year, you can access the service manual for your truck.