I would assume that you are using YaST (in SuSE9.1 pro) to install packages. Firefox is available as a package, and if installed via YaST, it should be a breeze. You first need to add a few online install sources such as
2. SuSE9.1 FTP
These sources have frequent updates for new versions of software. Once you are set up, all you do is search for the package in YaST, click and you will be off and running...