Depends what the little "plugged in device" is. It SOUNDS like it will be a direct swap if the plugged in device is the power supply for the LNB.
Hit the "-" key on the HR23. If it says SWM connected it will be a direct swapout.
Yes, the AM21 will work with the HR34.
Hit the "-" key on the HR23. If it says SWM connected it will be a direct swapout.
Yes, the AM21 will work with the HR34.