I beg to differ. I'm a Carpenter, and I can take one look at a project and tell you if it was done by a pro or a handyman. I have worked with many carpenters who are "union journeyman", but are certainly not pros. Though, we both got paid. In certain areas I don't consider myself a pro. For example, cabinet making. I can certainly make cabinets for you. However, it would take me longer than someone who does it regularly, yet a lot less time than Joe handyman. You probably couldn't tell the difference between my finished product and the cabinetmaker's (unlike Joe handyman). However, I wouldn't present myself as a cabinetmaker, even if you paid me. It's simply not worth my time and your money! So, no....being a pro is not simply about being paid.
One thing I have learned from this thread is that the standards for marine factory dealers is lower than I realized, having dealt with only one shop who's standards are high. However, come to think of it, I know of a boat yard who flies several factory banners including Yanmar's and I wouldn't let that yard touch my boat!
It may not matter who did it, it is history. The question is whether you want to have it re-done properly by you or someone else?