I don't think your extensions will be saved if you uninstall firefox. I've reinstalled the browser in the past and I'm about 99% positive I had to reinstall them after re-installing the browser. The bookmarks can be easily backed up like slipknotpsycho said. Just click Bookmarks>Organize Bookmarks... and then in the window that pops up hit File>Export...

Hope this helps.

edit: looks like you already got it... couldn't delete the post...