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Need new lock cylinders or your current keys are very worn down so don't push up and down the release pins
Keys do wear out, if they no longer have sharp peaks and valleys they are worn out
Drivers door lock usually wears out first, so if your key also has a hard time on the passenger side lock then I would say its the key that's the problem, a locksmith can sometimes cut a new key restoring the peaks and valleys, can't do that with a simple key cutter machine, it just cuts the worn out pattern
You can get new door lock cylinders with 2 new keys, but would have a separate ignition key(current key)
Or you can get a full lock set, 2 door lock cylinders and 1 ignition cylinder with 2 new keys, BUT...............1998 F-150 may have PATS, passive anti-theft system, if thats the case the new ignition keys would have to be added to the system by locksmith or you using Forscan software