Brother of thr Benz, ghj
You're on the right track, wanting to protect the new components.
The discant in the drier will absorb moisture from the atmosphere, but won't be contaminated from the system provided you don't engaged the clutch and put the compressor in operation.
If you must have ventilation, operate in the "economy" mode.
Your technican will finish servicing the unit by evacuating, holding at minus pressure to thoroughly dry the unit, check for pressure rise and finally charging.
Enjoy your efforts.
Happy Trails Beep Beep from The Spiderman in Houston!!!