Does your instrument cluster have a tachometer? The shift into o/d is accompanied by a roughly 25% drop in engine speed. That would be another way to know if the o/d in engaged.

If you decide to go the new bulb route, get enough bulbs to replace all of them. I have found that when those little bulbs have 10-15 years on them, the slightest jar breaks the filament.

With air bags the battery must be disconnected, and access to the back of the cluster may be more difficult.

I cannot recommend removing the ability to control o/d engagement. Too many times have I used the button to kick down to 3rd gear for a smooth change to quicker acceleration in a town environment.

Good Luck,

Bob

:>)