CrackMem vs BBSAK

Crackmem is a totally different thing, crackmem is an OS "extras" cleaner. BBSAK is... well mostly file manipulation. BBSAK should be compared to CrackUtil, which is similar, but crackutil for me is better at removing cods and sending them to the device. I just use BBSAK to backup 3rd party apps. If you want to upgrade the OS:

1-) Backup application data (address book, messages, settings,etc) using desktop manager, Backup and restore > backup button.
2-) Backup 3rd party apps using BBSAK option "backup apps".
3-) Download and install the OS you want. Remove the vendor file if its from a different carrier, usually located in the same folder as the loader.exe
4-) Use crackmem to remove unneeded files, and you can also check to remove some of them manually since crackmem sometimes doesnt remove "all" of them.
5-) Use loader.exe usually located in

C:\Program Files\Common Files\Research In Motion\AppLoader

to wipe/install the new OS and keep going until its finished.
6-) Restore application data using desktop manager, Backup and restore > Restore button, but read below first :b

That will pretty much do it straight forward. When using the loader select "Do not automatically back up and restore the device application data during the loading process". What it will do is that it will wipe the device, reinstall OS, then reinstall the 3rd party apps but it wont restore the data. You will restore the data after the whole upgrade is done using desktop manager.
You might also want to restore the application data using the advanced option under backup and restore in the desktop manager, that way you restore what you really need and not any garbage that might have been resting in the previous OS.