Write a listing of the directory to disk. Read the list with your spreadsheet program. Remove all columns but the filenames. Make a copy of the column with the filenames and apply all needed changes with global changes and/or commands (lowercase, replace spaces by underscore and so on). Add a column which contains the rename command for each file (something like rename oldname newname), according to your OS. Export this column as a file. Execute the file as a batch script.
Sounds more complicated than it is and is more reliable than manually changing more than 100 files.