Just replacing FF won't bring back your bookmarks, those are in a separate folder.

First Quit FF, make sure you quit, don't just close the FF window/s. Then go to the GO menu in the Finder, hold down the Option key and a folder called Library will appear in the list (this folder is now invisible in Lion so you can't get to it through the regular Finder method) click on Library in the drop down list and it will open, now double click the Application Support folder.

Now enter Time Machine and go to a date before you installed FF 13. Inside the Application Support folder will be a Firefox folder, replace your current FF folder with this one.

Next open the Preferences folder in that invisible Library folder and look for org.mozilla.firefox.plist, replace it too, relaunch FF. Exit TM.

For the banking app I don't know for sure but the first thing I would try is Quit iBank, then open that Library folder again in TM and in a date before you had the problem look for an iBank folder in Application Support, also look in Preferences in that Library folder and find any file that has iBank in the name, replace both files.