Lost key, what is the least expensive way to replace the key?

The cheapest way to do this is to replace the key and not mess with any other components. If you don't have a key, then you are going to have to get one not matter what else you replace.

If you put the ignition switch in it then you are going to need a key to go with it. So I would suggest just getting 2 keys programmed so that you always have a spare.

Let us know if there is more info to this if this answer doesn't seem to solve what you are dealing with. Below is the info from the manual to program keys if you need that.

Thanks