I assume that you have a SWM-LNB on your dish (since you mention the power inserter and don't mention any switch). If that is true the old receiver will not work.
If you have a SWM multiswitch, the old receiver would work connected to one of the legacy ports, but you'd still need to attach the power supply to the switch.
If you have a SWM multiswitch, the old receiver would work connected to one of the legacy ports, but you'd still need to attach the power supply to the switch.