Steering Failed problems of the 2005 Mercedes Benz E320

2005 mercedes E320 steering column wiring failure ( 'clock spring" & steering wiring module & srs air bag "failure). Partial repair corrected loss of turn signals, horn and speedometer at a cost to me ( owner of $749. ). One day later srs (air bag fail indicator) came on again. Back to dealer who said a wiring harness in the steering column is also bad & needs to be replaced at an additional fee of $516. But that they would do repair for $429. ??? did not affect repair yet. Just noticed defect investigation?? what should I do ?? (failure light for srs is still on etc. ). Can I recover (past $749) and future? ($516 / $429) costs???.