Yes, I think you should try Firefox again. If you have issues with it, post your questions in the forum, which I'm sure you would do.
Installing another browser and not making it the default browser does not cause problems as far as any of your browsers are concerned. But, the default browser is the one that responds to certain calls for a browser response. For example, if you use Outlook Express or some other email client on your computer for email and you click on link in an email to a website, whichever browser is set as default is the one that will open. Likewise, if you use Word or another word processor and have hyperlinks in such files, clicking on them will result in the default browser being opened.
So, to completely switch to using a different browser, you should set it as default. Normally, you will be prompted to choose whether to set a browser as default when you install it. But, if you elect not to make it the default browser at that time, you can easily do so later.
And, keep in mind, you can open and use multiple browser at the same time as long as your computer has enough memory. With my Vista laptop, I have Firefox and Chrome installed and, of course, IE is also installed. At the moment, I have Chrome set as default. Before that, I had Firefox set as default. And, again, I can open 2 or more at the same time but normally only have one open.