Headliner removal - 09 Aveo5

Greetings fellow Aveo owners!

I need to remove the headliner from my 2009 Aveo5 to install an NMO mount amateur radio antenna in the roof. To get an idea of how difficult it would be, I pulled the drivers side rubber door seals down and removed the plastic trim from the B pillar and back by the hatch on the same side. I can see up under the headliner and there appears to be some black plastic spacers that are glued to the headliner backing, and the headliner doesn't want to BUDGE...almost like it's glued to the roof somehow. I still need to run out and get a interior panel removal tool, so I haven't removed the two round plastic retainers in the headliner at the center of the car, and three more in the rear yet. If I remove these and the dome light/OnStar unit at the front will the headliner just drop down?

I found instructions for removal from an earlier year Aveo, but I'm not sure if they apply to my 2009.

Has anyone done this that can share a little advice?

Thanks!!!