2001 Ford Explorer Sport Trac Key Problem?

I have a 2001 Ford Explorer Sport Trac with 142K miles on it. I only have ONE key. The problem is the drivers door lock is acting up and being very difficult to use to unlock the truck. Passenger side and ignition locks still work for now. If I change out all four locks (Ignition, 2 door locks and the tailgate (hardly ever used and might not bother with. About how much would a locksmith charge to program two keys for the ignition switch? And how much to key all locks alike?

Try some graphite powder in the door lock cylinder first. They often only need some lubrication. Only use a dry lube in it though.Http://www.homedepot.com/p/The-Hillman-Group-3-g-Powdered-Graphite-Lubricant-703185/100137063

Remove the inner door panel, pop the non-working lock cylinder out and take that, plus a copy of the key to a locksmith, and stand back. My locksmith fixed my non-working door lock while we were standing there talking.

Way too much money!
When is the last time you lubricated your door locks?
Spay some penetrating oil in the key hole every 10 minutes for an hour You'll need to spray enough into the key hole to make a mess. Work the key gently left and right in the key hole until the key turns completely like on the passenger side.
If it's too ****** up the locksmith can just fix the drivers door lock or replace it. Call them for an estimate if you end up needing to.

Why not purchase a replacement transponder key now while you can? You should always have 2 for a Ford. As long as you have one, you can have a second one cut and programmed. Once you loose the factory key, you are screwed.

The program procedure for additional keys is right in the owner's manual - Ford does not try to hide it. It is DIY and you do not need a locksmith. You do need to follow the steps exactly as listed in the manual (or on-line if you do not have the manual). Personally - buy two if you can afford it. Long ago you could buy blank Ford transponders pretty cheap off eBay - but read on…

The only issue I've seen is that over time, it has become harder to get a store to cut a blank transponder key purchased off eBay. But Walmart will do them if you purchase the key from them and have them cut it.

Different models are different in their module location - not sure exactly on yours (beyond near the steering wheel on the firewall), but they do bury it just to slow down the theft process.