It's a very good idea to make a backup before you proceed. Please see Backup and Restore.
While in a View (default works well)...
- Select the player to be replaced in the main list.
- Select "Permanently replace Golfer with another player" from the Edit menu.
step by step wizard will appear describing exactly how to replace the
golfer with a new player or current substitute. You even have the
option to move the replaced player to the substitute list.