The "uninstall directions" if you can call them that say to mount the .dmg and run a script. Uh - guys 1.7.0 comes as a .pkg ... no mounting or running script.
You don't need to uninstall to upgrade, but if you want to uninstall, run the script from the 1.7.1 DMG, the script generally does not change between versions, it just deletes files. In theory.