If you're upgrading to stock firmware you just upgrade with the ipsw then run the jb after.
If you run the jb first well for one it won't work bc your fw isn't updated to the one you want to jb but also restoring to firmwares erase jailbreaks.
PLEASE HELP!!! I tried to upgrade through itunes before i ran the rednsnow.exe jailbreak and it said unknown error occured can not upgrade then it said i must do a restore i tried that and that said unknown error unable to restore.. Im at a stand still now.. Please help