Fuel System - low on fuel and idling, it eventually died due to fuel starvation.

What is your question?

I loaned my Bronco to someone who will remain nameless...my girlfriend :) 5.8W, F.I. that never had any prior fuel problems. While low on fuel and idling, engine eventually died due to fuel starvation as it ran out of gas. I'm told that what was added was "unleaded gas" but the engine hasn't started since. At the filler, what I smell isn't as pungent as 'gas'. She grabbed a red plastic fuel canister that had the "gas" in it. She has other equipment around her ranch that uses diesel fuel, but she's assured me that it wasn't diesel fuel that she put in. Other than the gas cap being opened briefly, the fuel system hasn't yet been opened. It's a back up vehicle, not my daily driver, and I haven't touched it in a year and. Whatever that fluid was, I suspect that it's now some hard varnish-like dried crud. I can (could the day I had it towed home) hear the pump when in ACC and ON. I suspect that to do this right, I'll have to drop the tank. If I have to drop the tank, I'll replace the pump at that time. When I replace the fuel filter....should I attempt to blow air from there back towards the tank? Is there some solvent that I should put in the tank hours/days prior to working on it? If there is a solvent to use prior, should I let it sit in the fuel line from the tank to where I've opened at the fuel filter....and then drain it after the solvent has had time to work? I want my Bronco back! This great truck has never left me anywhere and, although it hurts at times to feed it, I love it and want to keep it running for many more years. It's clear to me, even with my limited skills, that I should clean the entire fuel system from tank to injectors. How do I do that properly? Thanks in advance Aidan