2003 Saturn Ion Car not Starting in Cold Weather

I saw a few posts about car not starting in cold weather and was surprised I was not alone. If the
temp drops below 20 degrees F, I have trouble getting it started. I have already replaced the battery, and now the mechanic is telling me I have a bad ignition switch - and something to do with pass lock system, that the switch itself is not expensive but the labor involved with reprograming everything to a new switch (?) Is the expensive part. This issue came on suddenly and really do not understand it.