85 Coupe GT Lock Core changes

[Christian Hollyer and/or Mike Zappone <zappyer@tiac.net>]

The previous owner of my car had to change the tumbler set on my driver side
door, so now I have two keys, ignition passenger side, and driver side.

My mechanic (for those repairs not to be dared without professional help)
said you can set the tumblers to whatever you want so, the person who
previously changed had no clue, and should have set it the same as the old key.

I have to mess around inside the door and was wondering if anyone had any
idea how to do this?  Is it worth my effort?  Thanks.

ROCK!