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Question: Whats might be the problem here??

I have a 2007 Toyota yariz, with 70k miles on it. One day my car was over heating (red light came on) took it to sears auto shop and they told me it needed a new water pump as well as a new termestat. So I got it fixed and next thing you know my car kept over heating so I took it Back, they said the termestat part came our defected to they replaced it. Same dAy The car kept over heating! So I took it to another Macanic he added something to it that the car stopped over heating so I just drove it. Then about a month or more the car kept over heating so I finally took it to the Toyota auto shop they told me I had blew the head gasket and that my car needed a new engine! But then I read the papers they gave me, where it explaines the cost to fix it, it gave me the cost to take a better look at it and see if it really needs a new engine. So is it a possibility it might not need a new engine? Yes I do admit I drove the car a lot while the red light would go on. And I have a Macanic who can get me a engine with 6 month warranty and under 80k miles for around 900 with tax. He will charge me about 1,000 for the labor work. So I'm looking at 2k to fix it. What should I do? Advise! Please!