2000 Blazer Fuel Gauge doesn't work

I have a 2000 Blazer with around 80,000 miles, 4x4. Great vehicle but my fuel gauge went out quite a while ago. I haven't taken it in yet but have asked around about the issue. I was told it's not uncommon and can be difficult to fix. The gauge is usually on Full but will occasionally dive down to Empty and then goes back to full. Any ideas???

Thanks!