I think I would have a better chance finding a D700 Control Head than the RC-2000 Control Head. I am not sure where you heard of a RC-350 Control Head. --
Check the software download page on the Kenwood web site. If they have new firmware for your radio, just follow the instructions they have (also on that page) to install it. Basically, just connect a Windows computer to your radio and run the installer program. Kenwood makes it easy.