Help me get my Prius to run? please!

Hey guys i'm a freshman in college and i need your guys' help to save me some money.
I will tell you the story of my 2004 2nd Gen Toyota Prius.
A couple of months ago i purchased a 2004 Toyota Prius for $2200 with 170,xxx miles on it. It wasn't totally wrecked and looked completely repairable. It was hit in the front and everything under the hood looked like it was smooshed in. I test drove it for a little because i didn't want it to heat up as the radiator was busted. So everything is fine right? The car started, the motor started, batteries seemed fine.

Fast forward a little to where i put it in a body shop because i think all it needs is body work and a new radiator. Cost $1900 to make it look like new. New hood, bumper, radiator, headlights, etc...
So i go to pick up my car when it was supposedly read and it doesn't start
The dashboard lighted up but the motor would not start...

So i take it to the Toyota dealer and it turns out the battery was messed up and needed to be replaced, along with an inverter coolant reservoir tank, a sensor that's like hooked to the engine, and 4 fuses. They were gonna charge me around $6,500 to get it up and running again. I didn't have the money but i did buy the fuses and the reservoir tank because they weren't that expensive and i put them in myself.
So i took it back to my house and found some guy on craigslist who repairs batteries and brought him over to my house where he extracted the broken one and put in a good one for $1300...we tried starting the car and the engine STILL WOULD NOT TURN ON
at this point i'm seriously giving up and hate Priuses...well the guy told me the transmission was messed up...so i go and buy one with 37,xxx miles on it for $400 bucks and pay another mechanic to install it for another $400.

So i do the transmission fluid change on my own and try to start it...literally with fingers crossed that this car will hopefully start and i can begin to save money on gas. WELL, GUESS WHAT?! It did start but the engine turns off after about 5-7 seconds...

so my question is:

any of you guys know what could be wrong with it? i seriously don't wanna spend more money on this car. it i seriously screwing me over and sucking my college money out of my bank account. i bought this car because i thought it'd be easy to fix and i would save some gas but i has screwed me really hard.
why does my engine turn off after 5-7 seconds? and btw...the word "Problem!" appears on my navi system after the engine goes off. I WILL SERIOUSLY APPRECIATE YOUR REPLIES GUYS. I hope there is some serious Prius genies in here because i am getting depressed with this car. Please please please help me! i am desperate....

-Roy

 

please don't delete this thread mods...i am seriously in need of help with this car.