I had Best Buy off bunker hill install some amps and speakers in a car you don't just want anyone touching - many panels to remove etc
From research on a Benz forum when I was looking to do the job - many said they found a Best Buy with a level 3 installer I think it was. Fortunately the bunker hill had a level 3 installer then. Great price and great job. This was 5 years ago so might have to call around and see…..