Hi, you were on the right track. The silver plastic trim piece just pops off. Just be gentle and you should have no problems. If you email me, I may be able to send you some pictures that I have from when I took my gauge cluster apart to see what bulbs they were using back there. Unfortunately, they are LEDs that I can not access to change the color.
Hope that helps and good luck.
PS. Deff change it out yourself. very easy and quick to do.
Oh one last thing. I believe you need to remove the trim piece around the AC controls FIRST in order to get the trim piece around the gauges off.