I can't figure out how to turn on 3G! I'm on Kindle2I
3G ain't gonna happen. When running alternate firmware, the device is no longer (for all intents and purposes) a "Kindle." Amazon isn't going to allow a non-kindle device to gain access to the internet (through its various proxies) via 3G. There's no sense trying.
WiFi internet access on the Kindle 3 should certainly be do-able, though.