My Lightroom isn't importing all of a sudden and after digging through the forums it says to delete my preferences file and restart. I went to the library in my Mac, found the file and renamed it.
My question is: If I start LTR and it creates a new preferences file, will i lose all my presets, login Infoseek, publishing logins and all the other stuff that I've done to personalize my catalog over the year?
Yes, you will lose many (or all) of the customizations. Not sure which ones will be lost, but if it is stored in the preferences file then you will lose it.
By renaming the old file, you will have a reference for redoing all the preferences you want.