are the instructions on creating a new profile. Don't delete the old profile yet.
As for the moving information from one profile to another, I don't suggest the normal procedure. It will minimize moving corrupted information over. But you can move the information over manually and make sure that everything in the profile is new.
First you need to backup your bookmarks in the old profile. Go to bookmarks and then select show all bookmarks. Click import and backup and select export bookmarks to HTML. Save it to your desktop.
Now you need to redownload all your addons. To aid in that install Extension List Dumper
. Once you have installed that go to tools and then to addons. In the upper right hand corner there is a new button labeled dump, click on it. The screenshot below will show you the windows you will see. There are two drop down menu's on the right hand lower part of the window. If you select HTML in the bottom one it will assist you downloading the extensions again. Click the save as button. Once it is saved, shutdown Firefox and start it in the new profile.
Now import your bookmarks in the same way you exported them, just use the import function. Now open the html page from the Extension list Dumper. The links will take you to the pages where you can download the extensions. Save them to a folder, and once you have them downloaded you can install them all.
Now you will have a new profile with your bookmarks and your addons. If there is something missing, you can logon to the old profile and get it. Some addons have their own ways to export information. For instance the addon Athena allows you to export all the information that you have saved in it. Then you can import them into the new profiles Athena install.
Try this and see how it works for you. If you run into problems, just ask about it.