do people really trust these guys removing all the trim etc
It's like any franchise or dealer business, they are not created equal. Consequently, you depend on recommendations or chance it.
The only "trim" that gets removed, or should be removed is the trunk liner. Personally, I do this myself and leave it at home. Consequently all the rear inner wheel wells are exposed as is the floor of the trunk (where spare is usually kept). It is not necessary to remove the trunk lid liner. They can get past that piece without removal.