Firefox stores that sort of information inside a separate profile folder, which keeps track of all your personal settings, bookmarks, and history. This also means that it's kept separate from the install, so installing a new version shouldn't affect it.
To be absolutely certain, you can first make a backup of your places.sqlite file inside your profile folder, and then restore it if the upgrade doesn't keep it.
Older versions of Firefox used two separate files for bookmarks and history: bookmarks.html and history.dat. Starting with Firefox 3, however, they switched to using the single places.sqlite file. If you were coming from an older version of Firefox. It would be hard-pressed to keep it, but since your Firefox is newer than Firefox 3, you shouldn't have any trouble upgrading.