Renaming the file name (or part of the file name) from a list

I need help with a VBA/macro that will rename multiple files from an Excel list (1) rename the entire file name (2) rename part of the file name.

my path to the original file is C:\Temp\1234_customer#_$0.xlsx

(1) Change the whole file name to 4321_customer#_120.xlsx
(2) Change only part of the name from 1234 to 4321

Attached file is an example of the list structure for both of my problems.

Any help is greatly appreciated!