If out of warranty, don't force the handle apart
1. Remove reflector and bulb, remove bottom of handle
2. Drill out the pop rivet holding the bulb holder in place
3 Remove bulb holder, double check but the rear mounted switch is a push fit, front switch usually has a collar that unscrews, you should now have access to wiring which can be pulled through and replaced,
4. Assemble in reverse order, replace pop rivet, go lamping