Remove the lens, the bulb holder is held in place with a rubber ring, gently 'open this out' and the lampholder will pop out. The wires will probably not be crimped, observe the bullet, and especially the way the wire will be bent to hold it in place. Gently pull the two wires out - this will also remove the bullet. There will be a small circular rubber gromet through which the wires go, remove this before pulling the wires out of the back of the assembly.
Push new wires in, through the gromet, terminate in the same way with the bullety things then try to prise, force, swear - as the lampholder refuses to go back into the round rubber retaining rubbery bit...