Not sure if this is still helpful for you Ralf.
For a guide on repairing the screen of a Moto G5, see: [guide|112845]
Regarding your question concerning the compatibility of the G5 Plus screen to the screen of a G5: The screens have different dimension, with the G5 Plus being a bit bigger. As far as the comparison of repairing / changing the screen goes, this is rather the same for both, meaning there is hardly a difference.