Zampa, You'll be OK importing or exporting details from one browser to another as the original details always stay and it justs duplkicates them where you have sent them to.
A good idea, as a thought, you can also export Bookmarks or Favourites to a backup folder in My Documents so that should you ever have an incidence with a browser having to be reset you can always import the Bookmarks back from My Documents.
To do it:
Open My Documents, in the tasks on the left click Make A New Folder. Name it Favs Backup or something.
Open your browser and export as explained above but select the folder and click OK. The layout may look different if you open the folder that is because of the format they were exported in, not a problem.
Another thing with Firefox, it sets up a User Profile folder on your computer and stores the Bookmarks and lots of other things (Home page settings etc.) in it so that if you remove Firefox and install a more upto date version it already has your details .
dave