Haven't even looked yet, but is changing a headlight bulb on a '99 Astra a garage job? I know you can simply put a rear one in, but I'm thinking re-alignment etc on the front?
It is a reasonably easy job, small hands would be a big advantage, best done in daylight. From memory one side is easier than the other as there is a little more room. Changing the bulb does not affect the alignment, the lens sees to that. I think ensuring that I had the correct bulb was the biggest problem.
I have recently changed both headlamp bulbs on a W Reg Mk 4 Astra 1.6 16v. This was easy to do on the near side but more fiddly on the off side due to the access to the bulb holder being resticted by the location of the airfilter housing (this may be different depending on the engine derivitive). The bulbs are secured in place with bayonet action holder. My hands are fairly big but it can be done albeit a bit of a pain.