My N800 died a couple of years ago (I dropped it while it was charging, screwed up the charging cord, and motherboard at the same time). So, I can't remember anymore. But the N900 graphical package manager tools blow, big time,... Horribly slow in refreshing the repositories, few options,... It's certainly no synaptic package manager.
Manual install with dpkg for downloaded packages ends up being a dependency hunt... Command line apt-get is better, but there are multiple versions of the Fremantle extras-devel repository, depending on whether your on the Community update or not,... and which version...