You need to delete your part .fzp. I don’t have a mac, but on a mac it’s at something like ~/.config/fritzing/parts/user/LM324{blah blah blah}.fzp or something with a bunch of number and letters. Delete your LM324{blah blah blah}.fzp.
Open Fritzing back up, you should see a warning box stating, can’t find file. Don’ worry about it, it should automatically delete it from the .fzb and should not show up next time you open Fritzing
Fritzing is not that difficult once you get the hang of it. Just like everything else, it has a learning curve…