I've recently bought a 2003 A4 avant estate and the airbag light is on, after having it plugged in they found it to be the drivers side front sensor and the passenger side sensor. How much am I looking at getting them replaced? Is it an easy job to DIY? I know i would have to disconnect the battery first. Its due an MOT on the 3rd of next month and don't have the funds to pay through the nose for a fix. Any help and advice would be appreciated.