Upgrading JailBreak'd iPhone 3G to 3.1.2 firmware. JB'ing and unlocking it again.

This past weekend I upgraded my JB'd iPhone 3G from 3.0.1 to firmware version 3.1.2 Some apps were increasingly restricted to be installed only on 3.1.2 :(. So I had do it. Only thing that was stopping me from upgrading earlier was the pain I'd had to go through in restoring cydia apps. But there is solution for that too!
Just wanted to share what all steps I took to do it. This could be helpful for you too.

• Install AptBackup & OpenSSH from Cydia
• Once you’ve OpenSSH it’s safe to change the root password of your iphone from the default “alpine”. Google it to find it.
• Launch AptBackup & hit backup button.
• After the backup is complete using go to /var/mobile/Library/Preferences and make sure you see 3 back up files (aptbackup.cydiasources.tgz, aptbackup_dpkg-packages.txt and aptbackup_openssh.tgz)
• It would be a good idea to copy these files onto your computer using ssh connection. ( You could use winscp, 91 PC suite etc)

• Connect your iphone to iTunes and do a backup/ sync with you computer.
• Using iTunes upgrade the OS to 3.1.2
• In my case OS was upgraded 3.1.2 and baseband to 05.11.07
• Jailbreak iPhone 3.1.2 Firmware with blackra1n
• I downloaded blackra1n RC3 from http://blackra1n.com/
• Start blackra1n app (in my case it was on Windows XP) and click on “make it ra1n” while iPhone is still connected to my PC.
• Wait for iPhone to reboot automatically.
• After it reboots you’ll see blackra1n app on your iphone.
• Connect to wireless network (as you can’t use cellular data network yet, if it’s a non-ATT network)
• Run “blackra1n” app and install Cydia from it.
• Reboot your iphone and you should have a Jail Breaked Iphone
• Unlock iPhone 3.1.2 baseband 05.11.07 with blacksn0w
• Launch Cydia that you installed earlier on your iPhone.
• Press these buttons in sequence Manage -> Source -> Edit -> Add
• Input http://www.blackra1n.com as the source address then press Add button. Then press Done.
• Now press on blackra1n.com from the list of sources.
• Then select blacksn0w from the list of package and install it.
• Once the iPhone is rebooted you've an unlocked iPhone!
• You should now be able to connect to cellular data network.
• Restoring Cydia Apps
• Open AptBackup app (I don’t remember if I had to reinstall this again. But you could do so by following the steps described earlier).
• Hit Restore button and it should restore the cydia apps. (I didn’t face any difficulty in this. But if for some reason AptBackup can’t find the backup files, copy them back from your PC and try again.)

Now if you had cracked apps, go here and read this blog http://randomcritic.com/?p=161