First, make a full backup of your ROM using MTK Droid Tools. In the !Files_to_Flash folder that will be created, make sure you have a complete set of files. (Preloader, boot, recovery, secro, logo, EBR1, EBR2, system, fat, MBR, uboot or lk, cache, userdata)
Then, if you have CWM installed, make a complete backup with that as well. (this is for userdata)
To be extra sure, make individual app backups with Titanium Backup (can be downloaded from Play)
To update, you will need to flash the new ROM. Follow this tutorial about how to use SP Flash Tool
[Only registered and activated users can see links Click here to register]
be extra careful in every step, especially when you get to flashing. remember, there is certain risk in everything.
good luck. just post back if you run into problems