Firstly, welcome to the forum
You'd be after white LED kits for the car. You MUST make sure that they are the ones with the built-in resistors otherwise the car will flag up faulty bulbs.
If it's an RCD300, the easiest thing to do is to take it out and replace with something good. Even if you plaster up the hole in the dash, you'll get a better sound!!
There is an official ipod connection, but (a) it's expensive, and (b) crap.
Stubby aerials - there's LOADS on Ebay
Armrest - can't help as mine had one in it.
All the best,
Dan