I have a 91 Jetta and have experienced difficulty as well. There is a piece of black plastic in the way- I removed it and can now change the bulb with relative ease. I haven't noticed any problems with that part missing- .
Here is a link to a very detailed description. Not sure it applies to a '91, as it was written for a 2000.
http://mboedick.org/042/29/how-to-change-the-headlight-bulb-on-a-2000-Volkswagen-jetta-gls
HOW DO I CHANGE LIGHT BULBS
how are u? well u have to take out the head light clips which are on the sides of the head light then pull out the head light and uncover the second rubber cover i believe then reach in the head light and turn the socket to the left and and should come out the just change the bulb...when putting the bulb back just turn it to the right and put back the head light and rubber cover and the side clips and that's it...good luck
change a headlight on a 1997 plymoth voyager
how to change the rear tail light bulb on a 2004 Nissan maxima
To change the front head light you need to unscrew the screws to remove the protective casing. Once the protective casing has been removed the front head light bulb can be replaced with a new one.
I made a video on how to change the head lights in my jetta This is for a 2006 jetta tdi, but other years apply http://www.truezombielife.com/2006-jetta-head-light-replacement/
how do you change the head light time delay to 3 min. how to i get into the DIC information center, what steps do i take! (DIC)
right behind the headlight you reach in and twist the light out its a tight squeese but it can be done. be sure when you put the new light in not to touch the light its self.put the light back in, in the opposite direction it was removed
You need to remove the head light, which is rather simple, and reach through the opening from the head light to replace the light bulb for the blinker.
how to change headlight on 1999 Mercedes e350
what light?! head light, tail light, parking light, rear view mirror light, rear hatch light, underhood light, etc.
Unscrew it from the rear of the light. You may have to take it off to do this.