Wheel Speed Sensor
 

I took my 2006 MCS to the dealer today due to abs light, tps light and service engine light coming on intermittently. The dealer said I needed to replace found a fault for LF Wheel Speed Sensor and ordered a Pulse Generator. Does anyone know what might cause this to happen, what happens if I don't replace to Pulse Generator and is this a DYI project?

It likely will not have ABS and the lights will stay on
It can be hit by rocks ect or just died hard telling without the car to look at