I just replaced the pump on the SD as a preventative measure. The original pump was an OE pump, so, I presume it was original. Didn't appear to have any corrosion issues and the bearings were OK, so it probably could have went a few more miles. But, the SD got the full treatment over the last few months, so, the pump was on the block.

Nope, no harm in doing the flush if you don't mind spending the entire day at it. I would drive it for a few hours with the acid in the system. The heat must be set on high. When you flush out the acid, you will need to drive it and get the coolant flowing through the heater core, on every flush, so it's a long tedious process.

I don't believe that you can properly flush the acid without actually driving the vehicle with the heat wide open.