What headlight bulb will work/how difficult to change?

I own a 2006 Volkswagen Passat 2.0T and have always wanted to get halo headlights for it. One of my headlights finally burnt out recently so I figured now was the perfect time. I see that getting the full headlight with these bulbs in it is very expensive and a much cheaper alternative is just buying a halo bulb and installing that. So my question is, what bulb would be compatible (preferably white, I think it's 7500k) and does anybody know the difficulty level of installing these new bulbs in a Passat? Thank you very much.