When you change lenses on the Z7, will the CMOS sensors be exposed to dust?

You just have to be careful. I only plan on changing it once: to put the wide angle lens on it and leave it that way, but people have been changing lenses for a long time without too many problems.

That's what dust cleaning kits are made for.

Anyone know if it will be possible to buy the camera body alone? (And then add the wide-angle lens.)

The sensor in my Nikon digital SLR camera needs to be cleaned once in a while. Usually just a puff of air form a rocket blower does it, but I have had to do a wet cleaning. Before I blow off the sensor, I blow out the chamber of the camera.

Will I need to clean the sensors of the Z7? Or, is the construction of an interchangeable lens video camera such that the sensors are better protected from dust than is the sensor of a digital SLR?

I'll be coming to the Z7 from a PD170. I have never had a video camera with interchangeable lenses.