After carefully replacing the MMIC on the PCB, I tested the IF module by applying a 70 MHz signal again. This time the signal made it through all the way to the output as expected. So I put the case back together and installed the module in the DAR Plus receiver. And, as expected, the thing started working again.
And what do we learn from this? Never assume something can’t be fixed in-house. Any TV station should be able to to this themselves. And if you don’t have the necessary equipment, that’s also fine. Ship the device to me, I’ll fix it for a fraction of what the manufacturer would charge you.
Links and Sources:
 MRC DAR Plus, Vislink: http://www.vislink.com/
 INA-02184, HP: http://www.datasheetcatalog.org/
Now that you have fixed one you will be surprised how similar they all are. MMIC failure is very common and as you have found, fairly easy to track down. Many times the MMICs are from minicircuits and easy to get.
Good luck. I love repairing RF stuff. Have fun.
For the DAR, and Twinstream, you can replace the MRC YIG synthesizers with a Microwave Dynamics PLO-3000 DRO. Basically its a drop in; mount it, and size an output attenuator for it. Have not tried in DAR+.