the led's are plug in replacements for many dash bulbs in cars. I forgot the number off top of head. they have integrated limiting resistors, so no modifications to the harness needs to be made. I did the idiot lights as well (used white led's there), EXCEPT the headlight warning one. the resistance of that bulb is used in the RLU (reserve lighting unit) in normal operation, a very small amount of current flows thru it (it does in fact glow slightly, really only visible at night).
one thing I found out, and its a minor annoyance, is my neutral light is on all the time, and slightly brighter when actually in neutral. I think I have a problem in the jbox that is allowing some small amount of current to works its way into that lighting circuit. but if your jbox is working correctly (I KNOW mine has issues, as I had to bypass all the nanny stuff in it), it should work normally.
if I recall, the idiot lights where 194's. you can search the forum, there is at least one post with the proper bulb numbers listed.
I was going to do more work on the led's, but have since sidelined that project, as I intend on replacing ALL the gauges and idiot lights with a single combined gauge assy