If you send the DDE for flashing while the DP is installed it would be just a few days downtime. I reflash the DDE to the newest SW version before it is tuned, so not much to bother for later.
Some people try to fix different kind of engine management problems with a DPF delete, but this never worked good. It is important that all systems are intact and engine runs trouble free before a delete is done. Faults like active tank sensors, NO sensors, EGR actuator will be taken care of, but other problems with engine sensors or injectors have to be taken care of first.