Just curious, how did you go about replace your tail lamps with LED's. As far as the 'tail lamp out' light, the easiest thing to do would probably be to check the resistance of the OE bulb, then check the resistance of the LED assembly, and increase the resistance to that of OE. However, this may dim the whole assembly, so it may not be worth it.
As far as replacing the rest of the lights, there is a write up on how to do the gauges and radio lights on Gen 2's (and 1's?) The radio lights in Gen 3's are unservicable I believe. The inside lights could be a little tricky, but a little creative thinking should provide a plan. Good luck and please, post pictures!
Well all I know in the Gen.3 Taurus/Sable the type of bulbs that goes in the instrument panel are 194 and a smaller bulb which its the 74 which you could you could replace with better bulbs which are brighter. But in the Stock radio unit they can be changeable since the radio has an iluminated sheet panel so it has no bulbs. You could change the stock orange color in the windows swtiches which I think some people here have done it, I think Brad did to his car (Baby SHO). I think the other Gen. have the same bulbs but you could change the stock radio bulbs if it has some. You could buy the LED bulbs at eBay really cheap.
If you're going to replace any of your front lights with LED's you need to check your state's statutes for laws regarding color, and whether you can do that at all.
As for a how to.... i can walk you through installing LED's in your headlights and turn signals...
You also need to think of how you want them distributed and powered.... i put three LED's each in my turn sigs, and i can turn them off with a switch (in case the cops do a double take).... do you want your LED's clustered and maybe in a reflector for a directional glow, or do you want it like mine, where theres just a diffused color glow?