Need to replce the switch and key, how do you do this for a 1991 ford truck f150??

If you have the existing switch key,then turn it to acc-just far enough where the radio only works,push a paper clip into the hole directly under the switch through the plastic column cover,and wiggle the switch and pull on it,it will come out...if no key then pull off the plastic cover,try to center punch perfectly on the pin and drill the pin out,but drill very slow to keep the drill centered on the pin,and to keep the drill from breaking.be careful not to destroy the column around the pin,othrwise the switch wont stay in place..or you can hire a locksmith to pull out the old lock.