It's pretty straightforward.
Remove from car.
Remove from bezel.
Remove knobs.
Pry open.
Replace existing LED with a 3825 SMD LED of your liking.
Reverse process.
If you want it brighter, do a little ohm's law math magic to determine the threshold resistance for your LED of choice. In this circuit, they are modifying the forward voltage and current. You'll need the current rating of the led you're using and go from there.
I'm a vendor on another forum and have been doing led light mods on Chrysler/FCA vehicles for over 10 years. Let me know how I can help.
Here's a recent photo of the wife's 2005 RT Magum, with red LEDs and custom lighted pointers, in red.
View attachment 1704
Bob
Riverside, California