1997 RL 200k miles, the D4 light is out, is this indicating a transmission problem?
I cannot get any codes since the light is out.
Is this a simple bulb/led replacement?

Some times, not always, the transmission shudders in first or reverse at start up, especially when the car is cold.

 

It's most likely the bulb as that's the one light up most of the time. Especially with those miles if it's not been done before.