you can check resistance at the back of the fuel gauge and it should be about 20 ohms. but understand even if it reads 20 doesn't mean it is good once it gets hot and moves it might short out. There are certainly other people who rebuild gauges.
You will need to disable the internal limiter. then try the external limiter worse case the gauge is fried and it wont work, best case it will work fine.
I understand the frustration and yes that can be the result. I've been there - done that. I got tired of ripping the dash out and finally fixed it once and for all. I don't think when these cars were designed they were meant to be around in 50 years. Some things just have a limited life span...
