Incorrect - Goedel is not much harder to prove or wider-ranging than Tarski.
Goedel is proven as a corollary to Tarski in Manin, Course In Mathematical Logic (Springer - http://www.amazon.com/Course-Mathematical-Logic-Graduate-Mat...)
Strongly recommend Manin to the mathematically literate interested in a sophisticated and worldly introduction to logic. Manin gives very understandable details of the Smullyan proof this guy is taking bits and pieces of.
-- And Antoly's "semantic/syntax" distinction is overdone.
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