Is using a live cd a good idea? Will it keep the rest of my computer including storage and installed OS safe?
Well, I think you should further tighten the security up more, my suggestions are:
- Get into Safe Mode (if you are using Windows OS)
- Fire up VM software, and do the process in there
The best is do it on Linux OS. Even though imho the malwares from phones are different from the PC ones.
You are right to be cautious.
Android malware cannot directly run on a Windows PC. Android malware CAN be used as a dropper for Windows malware, however, and this is why you should be careful about hooking up your phone. But there is one method of restore that should be safe:
Boot your phone into Fastboot mode (sometimes called 'bootloader' mode) and use the fastboot command on your PC to either:
a) Flash your new image directly (usually only works for OEM images)
b) Flash or tempboot TWRP and use that to wipe your phone COMPLETELY (remove /system, /data, cache, Dalvik cache, the works) and transfer and install your new image. (usually works for custom ROMs). You can use ADB safely here as well.
Even root-access malware cannot mess with fastboot, and by extension a booted-from-fastboot recovery partition, so you should be safe restoring your phone like this.