It is a fairly straightforward job on most cars, BUT......
a few years ago, I needed to change a headlight bulb on a Vauxhall Zafira (W reg). As luck would have it, I was passing a Vauxhall dealer, so I got the replacement bulb there and tried to fit it. I had to go back in and ask if someone was taking the you know what. According to the owner's manual, all you have to do is unplug the lead, rotate the bulb holder and remove it, insert new bulb,and replace. This would be fine, were it not for the fact that the indicator light assembly is smack bang up against the back of the headlamp bulb holder, making access, let alone removal, impossible.
It took me and a Vauxhall fitter (!!) over 25 minutes to replace the bulb, which involved removing the indicator light assembly, part of the air ducting, holding the ducting housing out of the way so the fitter could get his hand in to remove the old headlamp bulb..............