I have not seen a Nanawall slider up close, but my Eurowall multi-sliders need to have the door panels removed, from the tracks, to replace the rubber gasket all the way around. I would want an experienced dealer/installer.

That "silly" rubber gasket makes a huge difference in how much heat/cold and sound gets into the house.

Here in the NY area these are installed by us and other glass shops all the time. I would look up a glass storefront shop locally in Google.

If you're balking at a $500.00 trip charge, you've self-excluded from them as a customer, exactly why they put the charge in place. Good for them.