There are several ways to attempt the upgrade. Our docs present one way. What I usually recommend is to install the new server (9.0) on it's own, then export ALL from the old server (either via command line or the UI), then import that export into your new 9.0 server. With no customizations, this should work ok. If your test worked and you've tested all your reports and resources, you should be fine to continue down that route as well. Good luck!
-Mike