First: It wouldn't hurt to have a spare motor on-hand, it might prevent your loco from becoming an expensive shelf queen someday. This would be a parts purchase, not a warranty claim. I'm glad to see that Lionel used a U-joint between the motor and the worm. Hooray for LionDrive!!
Second, I agree with Pat (harmonyards) and PSM that at least some of the noise is coming from, or is amplified by the slotted plastic tach ring. The "bzzt" noise at -0:06 in your first video is probably something inside of the shell rubbing on the ring.
The flywheel is attached to the motor shaft by two set screws. You could try loosening the set screws and re-seating the flywheel by gradually tightening each one (like torquing down the head bolts of a small-block Chevy.) While you have it off, look closely at the tach ring in bright light... does it have any cracks or splits? Also, does the motor still make the noise with the flywheel and tach ring removed?
As Pat said, it's prudent to put a drop of oil on the motor bearings where the shaft exits at each end of the "can."
In your case I don't think the brushes are squeaking. If the brushes are fresh and square (as you would expect in a new loco), and if that particular motor has a commutator segment or two that is "high", sound may be produced as the brushes bounce at the edge of the high segment. If this is the case and you turn the motor shaft slowly by hand you might feel it "stick" slightly. The brushes will eventually wear concave to conform to the commutator. But if the commutator does have a high segment, you'll get arcing. The motor might not last as long or perform up to spec.
My $.02. I like the way the loco is made and it should be a great performer, I wish more of them were made and geared like this!
