If anyone has questions regarding the n900 then please ask, I will try helping you out if I can.
The latest firmware PR 1.3 was released a few months ago for the n900, I personally prefer doing a clean install of the firmware by flashing the device but you can always update with the Nokia software updater.
Flashing the device is a piece of cake and nothing to worry about other then your power going out during the flashing process.I have flashed my n900 about 5 times now including the EMMC
as far as the lock code is concerned, I think the only way to get pass is by re flashing the emmc but you may find a better alternative by searching google or threads at maemo.org
The latest version of NITDROID is 0.9 that is build on gingerbread, you can try turning your device into portrait and click the skip button to skip the setup. Android lags a lot at the stock speeds so I suggest you to over clock your device to about 900mhz to achieve usable performance.