Who did you purchase the engine from? Did they give any warranty? Even most junk yards will give a 30-90 day exchange warranty. Talk to whoever you got it from and see if they'll do the right thing and swap it for one that runs.
You'll be out whatever you paid for labor, but you would still be better off.
As far as doing it yourself, it's a big job (time) and unless you have proper tools, difficult.
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