I switch out reservoirs from an in place Quick-Set all the time. Seems I can never replace both at the same time. Never had a problem with it CAMAJohn.
I've done this many times also.
I usually have extra tubings, so I fill a new resevoir and new tubing without changing the quickset. After I do rewind, and prime to fill the new/replacement tubing, then I simply connect back to the quickset. No additional prime for the canula.
Then next time, just change out the quickset, connect the tube, and then prime (fill) just the canula.
When doing the rewind, and refill, be sure to be disconnected from the quickset !
Everyone does that. I refill the same cartridge several times during the three days I have the set in, that's why I have so many reservoirs.
Okay next question is how long have you kept a Quick-set before changing it out?
I personally keep to the 3 to 3.5 day rule.