If you can explain exactly what is happening I may be able to help you. I'd suggest removing the battery cables and reconnecting. turn key to run position without starting. does the radiator fan come on? Try to start the engine if the radiator fan does not come on, does it start and run for 3 seconds then shut off? does the engine just crank and no start?

you mention that the tech says the engine tried to start after disconnecting the battery and reconnecting but "just barley, then it went back to nothing", what does that mean?

I'll try and help point you in the right direction but full disclosure, I AM a dealership tech :P