For my tune the local WA Roo agent did the tune, they did it in one day and were talking to the Roo tuners in Brisbane the whole time.
Road test before and after.
I would not be happy sending the ECU away. You should be able to get your selected tuner to do it locally.
Re the exhaust, I don't believe you need a retune, the ECU adapts the fuelling within its new parameters to account for the different mass air flows.
Apparently a properly designed 3" system provides much better air flow lower EGT's.
I haven't heard a D4 with it fitted, but would definitely do so before deciding.
Just my thoughts.

