Sounds like you want to do a full conversion...
For the most part: you can replace many bulbs with LED replacements. I purchased all mine from
http://autolumination.com
As far as the turn signals go: I would do some research before you blow all your cash. The 03-06 Elements had a common problem with the turn signal system... basically, LED's draw less power, so the system kept thinking that with out properly drawn current from incandescent bulbs, that the LED bulbs were 'burnt out' creating the rapid blinking effect to indicate the driver. There is a fix to this, where you insert something in the turn signal line that evens out the current drawn to fool the system. I've never worked with it but hear it's something you have to do if this happens to you.
I can't say the 07's+ will have the same problem, but it is something to consider. Easiest way to find out: buy one and try it out. After the first time you turn the signal on, it should happen if it's not going to work. If it doesn't, and just works, then you're good to go!
Map lights: 194
Dome & rear light: Festoon 44mm aka 578 (get 6+ wide angle LED's, 120°)
Gauge cluster: Not sure what you can do for a 07+
HVAC controls: considerably more complicated, not a drop-in replacement
License plate lamps: 194
HID headlights: Let me emphasize this fact for everyone who is considering an HID conversion...
HID's are not intended for reflective headlight housings
HID's require projector housings to focus the light appropriately. Placing them in a reflective housing will scatter the light everywhere and create a consistent high-beam effect with no improvement on road illumination compared to the project housing. Additionally, you will be blinding on coming traffic and is technically illegal. If you're willing to spend the money, doing an SC front end conversion will give you the required projector lenses for the low-beams and supply you with halogen high beams which are recommended for such set ups. HID's require a full 30 seconds to reach maximum lumination, and are not designed to be turned on/off like high beams for all the purposes they serve. The end result will be a unique looking E (as SC's are rare enough as is) with the advanced functionality of HID's as they were intended to be used.
If anyone ever has any questions, please feel free to contact me.