I think I know the answer, but how much of a pain is it to replace it?
Does anybody have the process?

I imagine the whole cluster has to come out to get to the back of it...and then some.

 

do a search for odometer backlight, there is a good write up on taking the dash apart and maybe even a bulb part # somewhere that I remember seeing. I have the same issue but I have not had (taken) the time to change the bulb. Dealerships will tell you that the whole cluster will have to be replaced.

 

Give it a few months it will come back on. Just playing, but mine went out and exactly two months later the stupid thing came back on. Been working since Jan for me.

 

I was able to find a thread outlining this repair.

It was an easy fix. Probably 45 min or so. Two screws on the lower dash panel. Two screws on the upper dash panel. The upper dash panel slides towards you to release the clips. Four screws holding the cluster to the dash.
I just lifted thin the plastic backing shield off the corner near the odometer bulb, replaced the bulb and put it back together.

The hardest part was finding a bulb (Sylvania 37). They're tough to find on the internet, and then most places whack you with shipping. I finally found an Advance Auto Parts near me that had them in stock. It was the 4th one I checked.