On the PC board next to the part there is usually a component designator in white ink.
If the thin' that you are describing is the thin' that I thin' you are thinking about then I thin' that there should be a designator like "L4" or "L14." Using that designator you can check the parts list and find out what the part is and buy a new one.
It looks to me like the red thing is the tuning slug in a tunable coil and even if you replace the coil, the radio will have to be adjusted with the new part to work right.
Since you don't seem to know about component designators, and don't recognize that the red thing in the square thing is a tuning slug for a coil, you'd probably be better off sending the radio back for repair.
Learning electronics is good. But this is not a very good way to start. (too complex)