My local HRO sells the control head for about $100. AFAIK it's a direct plug-in, no other changes necessary. The PC program that comes with the R1500 is different than the PCR1500 though, and you'll need the R1500 version to program the memory channels into the control head.
You can program it manually but it's a HUGE pain - since there's no numerical keypad, you have to select the frequencies by twirling the tuning knob.