Here's what you should do:
1. Immediately call a roadside assistance service or a tow truck. This is not a DIY fix.
2. Do not attempt to start the engine. Doing so could cause significant and costly damage to the fuel injectors, fuel pump, and other parts of the engine.
3. Inform the roadside assistance or tow truck operator that you accidentally put gasoline in a diesel tank. This will help them prepare appropriately.
4. If possible, try to prevent further contamination. Don't drive the truck at all.
The only solution is to have the fuel tank drained and thoroughly flushed, and possibly replace contaminated fuel filters and lines. The extent of the necessary repairs will depend on how much gasoline was added and how long it sat in the tank. The cost of this repair could be substantial.
