Looks like the indy hacked up your harness, installed a cheap atermarket amp with rca/high level converters. I'd have an estimate made to make it fully right by the dealer, including correct DSP amp and harness repair... Then have the indy pay the bill to fix what he screwed up and refund what you paid him, taking back his parts once removed by
qualified technicians. Blatant hack job, obvious butcher. I'd strongly consider not using that shop for anything in the future.
And everything Brian-BMW has said is spot on.