you dont need to take the bumper off with the "normal" lights. In "normal" lights theyre H7. I changed all my bulbs at once, be prepared for scratched hands. For the OEM+ look i usually put 6K bulbs in mine, its a nice sharp white, with a very pale blue tinge. I have used 8K before, but they where a little too blue for my liking. IRRC 4500K is the whitest you can get, but might be worth double checking online.
Its the same as changing a bulb, kind of. Where you plug the cars harness into the back of the bulb, you put the kit inbetween. When you have a look its self explanatory. The O/S is easy enough to do, you might need to wiggle the washer filler out the way, but plenty of space.
THe N/S is a bit more of a ball ache. You need to undo and remove the solenoid thing (for the air intake) and also take the battery/fuse covers off. You can squeeze your hands down and in then to change them. I put the ballasts inside the battery box (inside another little plastic box i had lying around)
I tied the N/S ballast to underneath the slam panel to make it nice a neat.
Done loads of them now,on various different cars (mainly VAG tbh)
Any more help drop me a pm
I'l see if I can word it better for you lol