Replacing Fuel Gas Cap and Ignition Switch

[Gnasher]

Both these locks and the problem with them being difficult to turn is a well known old issue.  What often works is a good clean out with something like WD40, flood them, then dry them out with brake cleaner, finally a good dose of dry grafite.  When you use each the trick is don't push too hard and turn slowly with a slight up and down motion to get a better feel.

Give that a try first, before you go the replacement route as that can be very costly and difficult, many pattern replacements either don't work, cause ignition faults or just fail in very short order.