How does it look internally? If I do a Google search of the difference will it come up clear as day?
Probably. There are several diagrams of the Series 80 internals around, but I don't have any links.
The additional changes made to the standard parts are as follows:
Firing pin. Extractor. Grip safety. Firing pin stop. The firing pin springs were shorter and softer in the Series 80 pistols, but the reason for it is uncertain.
I have theories, but no hard proof. All these parts are interchangeable with Series 70 and pre-Series 70 pistols, but not vice-versa. The firing pin springs are fully interchangeable, as are all other parts.
The Series 80 hammer came with a flat quarter-cock shelf instead of the original captive half-cock notch. Simpler and cheaper than machining the captive half-cock, and almost nobody was using the half-cock as a safe carry mode any more. Interchangeable.
Most aftermarket firing pins are the Series 80 type. Ed Brown is the notable exception, and both types are offered.
Series 80 slides will work on pre-Series 80 frames if the plunger and spring is removed, and Series 80 frames will work with pre-80 slides if the frame blank is substituted for the frame levers. It also goes without saying that if the Series 80 pistol is "De-Lawyered" that all standard pre-80 parts can be used.
Additionally, about the time that Series 80s were introduced came a change in the hammer strut design. Stronger and more durable than the old struts, but less useful as a punch and slave pin. Also interchangeable.