Henri-yamaha

Hiya, i have a yamaha DTR SM 125 my headlamp doesnt work and i am trying to find out how to replace the lightbulb. i have taken the fairing off but i cant seem to get into the headlamp. can you replace the lightbulb or do you have to replace the whole headlamp? if you can just replace the lightbulb what lightbulb do you use? thanks for your help guys