67 Cuda Formula S commando V8

I’ve been lucky enough to score a nice performance indicator, and want to swap out my blank gage. I know it is attached by 3 screws/bolts. Been told I can swap out my blank without removing the dash. Anyone done this? If I have to pull dash, what suggestions do you have on other parts that I should replace? Bulbs already on the
I assume any vacuum source is ok?