The LEDs do dim. I order my LEDs from dealextreme.com because its cheaper. You need to pop off the interior lights and measure the inside to see what will fit and purchase the led panel that will fit inside. The panels usually come with universal adapters.
These usually work with the license plate lights
These are for the interior
They are much cheaper on that site so I just buy a few extra ones and see which one I like. Whatever I have leftover I just give them to people. They love them. I'm also looking at a LED reverse bulb but I'm not sure which connector the reverse bulb uses. If its T10 I want to get this one.
If you want to buy from a company that is known for LEDs and will have warranty but cost more try
Dealextreme is just an organized ebay really.