Note: There is no upgrade you can purchase that changes this. There is no FTP access to free hosted WordPress.com blogs and we bloggers cannot install any plugins. To have plugins and Google Analytics you need to hire a web host and set up your own self hosted WordPress.org install. See here for a comparison. http://support.wordpress.com/com-vs-org/
fwiw: if you set up a free account at Site Meter, you’ll have access to a lot of the same material Google offers. The upgraded paid account will get you more stats. Both levels are HTML friendly, and easy to put into a widget in your sidebar.