It really wasn't a big deal.
1) Installer drilled into the frame and installed two metal square 'tubes' (not before painting them with rust free paint);
2) Installer bolted 62 kWh battery onto those two square tubes and other fastening point adding in some extra long bolts in the process.
3) Installer bolted 62 kWh battery as well into other attachments points, slightly modifying / cutting underplastic to fit
4) Installer uses Dala canbus adapter
5) Installation labour included Dala canbus adapter
Note * This did not affect my plans to put in 2" hitch for carrying Ebike
The range is fantastic; I almost wonder if it's better than in the 2019 Leaf (is it because my 2011 is lighter? or am I just imagining?), or maybe it's not better. I do know for certain that I drive the car, often 75 -80+ mph on the 101 freeway in Southern California. I do this with permanent surf racks and usually carrying around a 55lb Ebike