well, for starters, Halos are WAY more involved then the HID upgrade.
the HIDs don't require the removal of the entire housing just the dust cover from the low beam.
now for your halos:
drop the front bumper, remove the entire headlight assembly, bake assembly in oven to loosen glue, gently split front from rear housing.
now you can add your halos remembering that you need to drill for the LED wires and not to get any glue on the chrome parts (unless you are doing a flat black treatment at the same time)
with housing apart, tap the parking lamp wires for your Halo leads. temporary replace housing into car and test. final solder electrical connections (you remembered to put heat shrink tubing on before you soldered right?)
now re-bake the housings in the oven till glue is soft again, re-assemble headlamp making sure its sealed all the way around, replace in car, replace bumper, wonder why you have an extra screw (lol)
now don't you wish you just spent the 1 hour to put in the HIDs and left it alone?
if you are going to take the time to crack open a headlamp you might as well go all out and to a BMW A4 Bi-Xenon assembly retrofit while you are in there. just saying . . .
