Performing an update of your camera software seems like the difficult job that can only be done by experts. Nothing could be further from the truth. If you can copy a file to an SD card you can perform the update. Certainly for the use of Nikon P lenses you should definitely do this. But it also has more benefits. Many improvements are made to your camera when you install the latest firmware. You can see an example below with 1.03 to 1.04.
Update from 1.03 to 1.04
• Added the following AF-P lens support: - If the standby timer expires after focusing, the focus position will no longer be changed when the timer is reactivated.
- If the focus is adjusted by rotating the lens focusing ring, the focus indicator in the viewfinder (and in live view, the focus point in the monitor) will now flash to indicate when infinity or the shortest focus position has been reached.
• The following problem has been resolved: - Optimal exposure was sometimes not obtained in photos taken in live image using an electromagnetically-controlled aperture lens (type E lenses).
This way every update has its improvements. How that works is a whole story to describe, that's why I have picked out a clear video in which it is all explained. It works practically in the same way with other Nikon cameras. During this process your camera settings are saved, so you don't have to stop that.
You can download updates for the D7100 from the Nikon Website.