You didn't answer the question. There's a HUGE difference between replacing an LCD assembly, LCD unit, and the glass on a MacBook with a Retina display. The first one, as you say, is easy. The second one very difficult and risky. The third one is practically impossible, unless you have some serious and expensive equipment.
If you can replace the glass only, there a multimillion dollar check with your name all over it and way more business than you can handle.