mazda millenia ignition

Your ignition lock/tumbler/cylinder is one piece. Replace the cylinder and you replace it all.

with the condition I stated above, could I fix the problem just by replacing the ignition switch and tumbler only?

The tumbler is located inside the cylinder and is not a separate item. You HAVE to replace the cylinder in order to replace the tumbler. When you by the cylinder, the tumbler is inside.

EC is correct, you are referring to the barrel & key assembly, the ignition switch is separate, the problem will normally be with the barrel & key assembly.

mark (mhpautos)

I searched the part online and I have one which is IGNITION LOCK CYLINDER for $330.00 with a picture showing an assembly with keys, and another listing called IGNITION LOCK & TUMBLE SWITCH for $144.00 with a picture showing like a white plastic connector. I just want to know whether I need to have both of these parts to solve the problem.

The plastic piece is not a tumbler. Maybe the just worded it wrong. That is really a switch that directs voltage to which ever circuit needs it according to the position of the key. (acc., On, Start) It's quite possible you'll need one or the other, not both. If the key is hard to turn, then it's the lock cylinder (tumbler). If it won't start, or acc won't come on, then it's the switch.

the car starts easily while you turn the key to the ON position instead of the START position and then make that squeaking sound until I turn back the key backwards a little bit towards ACCESSORY position. I also get that squeaking sound briefly sometimes when I turn the key to the OFF position. So would this tell me that the problem is then the switch and not the cylinder?