I just got my 2 new G5s, there wasn't much transition training for me I read the manual and went out flying. The biggest difference for me was the location and display of the CDI and Glide slope as i was used to looking at a traditional CDI off to the right.
The other thing I would recommend is sit on the ground and go through all of the options you can get to with the knob, as some of the initial functions are not 100% apparent. (I ended up doign thsi backwards and set on the ground after my flying as could not wait to test the G5s out in the air. Below is a pic of mine in flight.
View attachment 78738