sitting on fence about amp meter

How simple the conversion is depends on what inst' panel it is. I wouldn't go into some inst' panels for this gauge conversion alone. A better plan would be to renew and or upgrade all of it at one time whether thats before or after it breaks.
Out of the millions of them used only a small few ALT' gauges have failed. A lesser number of those have actually caused fires. The internet spreads bad news and BS like wildfire.