What you need to do is create a 2nd PSN account. That will be where you do your modding. After exporting it to ps4 mail the items you want to your main account. This prevents you from overwriting your main account and resetting any new achievements or items that you've gotten.
This has been covered in NUMEROUS threads and would do you well to search the forums.
This has been covered in NUMEROUS threads and would do you well to search the forums.