Dude, it can be done with everything in situ, but its just bloody hard. If possible, draft in a child or a friend with childlike hands!!
Believe it or not, whipping the headlight out is the quickest and easiest way - I got it down to a fine art in the end!!! You can have the bumper off in under 5 mins, headlight out, change bulb and all back together in under 30 mins.