Just did an LED swap for the trunk and dome (2nd row, no sunroof) lights on my 2014 SL AWD, without the Premium package.
Here are the parts that fit. Both can use the same bulb, but due to availability at my local shops, I had to buy two different ones from two different stores which were across the street from each other.
Bulbs that fit are the 3021/3022 model. Both are 30mm Festoon and fit perfect. Each below are in the $12-14 range.
Sylvania - PN # DE3022LED.BP - This one I used for my dome, it has a whiter light than the front domes at 6000K, but close enough. It has white shell covering the LED, which makes it a little less bright than the Phillips. This one is available at Autozone.
http://www.autozone.com/autozone/parts/ ... 302200_0_0_
Phillips - PN # 129416000KX1 - This one is very bright, looks like the custom 3175 setup that someone did in a previous post, but no customization and fit is perfect. I used this one in my trunk and it was bright, much brighter than the Sylvan, since it doesn't have a white shell covering the LED. This one is available at Pep Boys.
http://www.pepboys.com/product/details/928812/00825
I do recommend that before you remove or add the bulb, that you unplug the switch from the electrical connector, this bulbs are so small that my fingers could potential short the positive and negatives as I am trying to pull them out. I would hate for someone to get shocked doing this.
Hope this helps...