"What is the reccomended mileage interval for changing the key lock cylinder out? What is involved in doing that? Will I have to have the car re-keyed? (hope not, I have 3-4 sets of keys for it now)."
I changed mine out at about 110K due to starting to have some issues with it. It is not that difficult to do and I bought a cylinder that came with instructions how to make it work with the original key and the whole process of replacing the cylinder. Takes a little time to figure out the first time but, hey, now I am a lock smith :-) I will try to find a link to send you to where I found mine.