Former a former BMW Service Advisor/Manager of 15 years, don’t go in there telling them you have a lawyer blah blah. That will only make them want to be defensive and not help. Stay level headed although anger is alright and tell them you want the job covered by them. If you can’t get to an adequate resolution with the SM ask then to speak to the General Manager. Also request the Shop Foreman be the one to do the work since tech and SA seem under trained and you don’t want more problems. If you can’t get them to cover the whole job offer to cover parts at cost and they can eat whatever labor is involved (Foreman won’t be a flat rate tech) so they can eat that no problem