97 210 IR Keys dont work
 

For some time my smart key stopped working (key turns the starter but engine wont kick over - the defeat circuit is working), so I used one of the flat keys to start the car. (The door open feature still works so I use the smart key as a key ob. Now my wife's key (the second smart key) stopped working and the first smart key is working again.

I am afraid it might the column electronics, unless someone has some ideas.

How much does the mechanism cost and can you use your old keys? CAn I do this myself or does it need to interface with a MB computer to work.