To answer your original question it's not too hard to swap the OEM components. The biggest issue is getting them without sacrificing your first born as each housing MSRP's for about $800.... not including the ballasts, lamps, or the wiring adapters you'd need for the D2S lamps. Plus if you wanted to wire up the leveling motors you'd need those, some spare wire, and the leveling switch for the inside of the car. So while possible unless you found some somewhere cheap I'd just go with the kit for the moment.
The whitest color temp is 4300k. This is what all OEM HIDs are. I don't recommend going with a higher kelvin rating just to get that "blue look" as the higher your kelvin rating goes the less actual light output you have. If you're looking for the blue "flicker" you see on higher end cars then you should do what many members (such as mr_mazda and myself) have done by retrofitting a TRS clear lens in to replace the OEM frosted lens, space the lens, and a few little mods to the shield. This will clean up the cutoff significantly, reduce glare, and give you that pretty blue color while still giving you the most usable light. I'm also using a DDM 35w 4300k kit with TRS lenses and shield mods and I highly recommend doing this if you're adding HIDs... makes a huge difference. I can't find any of my lighting pictures, but the results are basically what mr_mazda posted.
As far as melting things goes you won't have to worry about that with the 35w at the very least. The stock H7 lamps are actually 55w, so really you shouldn't have any issues with a 55w kit either. The real big decider between the two is how/where you drive. If you drive in a city a lot then you don't need 55w lamps. If you're more outside of lighted areas or driving back roads a lot then they might be more to your liking.