I would replace them all.
It's the same thing I did when one of the bulbs in my instrument cluster went out.
You go to a lot of trouble to pull the cluster out. With my luck, if I replace just one bulb, as soon as I put the car back together, another one will go out.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".