Just thought I'd update this: For Iceweasel 3.5.8, It's just as straightforward as you'd expect:
1. Open Synaptic in Easy Debian ("sudo synaptic" at the terminal)
2. Type to search for iceweasel
3. Click the little icon to the left of it, choose "Mark for upgrade"
4. Apply, download, install, have a nice day.
If you have trouble downloading packages from http.us.debian.org as I did, edit your /etc/apt/sources.list and replace "http.us.debian.org" with "mirrors.kernel.org", then run "sudo apt-get update" and try again. For the noobs, DO NOT attempt to install unless all packages were downloaded successfully!
