Gas Gauge went crazy

So on Tuesday, I took my truck to toyota because my gas gauge would say I had an empty gas tank but then slowly moved back up to it's actual amount. They called me to the service garage and asked questions about my dvd player and alarm. Like who installed them, when, and how. Then they said the shop that wired those things might have tapped into a wrong wire and it's causing the sending unit and fuel pump to lose power. But of course that would mean the truck would die on the road and it never did. So he said that my bill was going from $55 to $220 just to keep looking for the problem. I said fine and I left. He called me back this morning and said there was a short in the cluster itself. They're ordering me a new one but I have to wait until maybe friday to get it back. I just have to pay a $100 deductible for my warranty company. Not perfect but it's better than having to pay the $220 diagnostic.