How do you remove the key lock and tumblers 1972 Pontiac?

you needto have a key in the slot then look all arounf the outter edges of the finger grab points.You will see a pin it is very small.With the key in you depress the pin and turn the entire assembly.It will pull out when you feel the release. If you have lost they key then a lock smith will need to make you a temp and he will usually have a new one with him.I had it done five years ago and the cost was 65$