You need to backup your modem first, because if you don't you may break your 3g connection and have "SIM card not found".
But please don't flash anything before I have a "modem.bin", then I'll test it !
The procedure to restore the modem you backed up is a little more complex, and I'll prepare a script for that...when I'll be sure it's working 100%!
I must do it, only because I was stuck in a bootloop and lost 3g.
the other option is to backup your full NV partition as explained in the QPST thread, then restore it after flashing the new rom...that's the safest way actually !!!