i have a1991 sel 300 when i try to start the car the key will turn to the start on 1991 Mercedes-Benz 300SEL

position but not turn any further what is the problem?

Asked by for the 1991 Mercedes-Benz 300SEL
The key tumbler is locked up and needs to be replaced.
where and about how much for another one and what is it ahard job to do ? thanks
It will require some special tools for replacement. Unless you have an extensive tool assortment then it is best to have a qualified tech do it. Call around for estimates and ask your friends who they recommend as a good shop to use.