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Timthumb seems simple in itself, but integrating it into an automated system is another story. See here: Timthumb Technical Support
His prices are quite high — I expect he wants to limit his time on the project — and other freelance coders would likely do this for much cheaper. However, it is along the lines of a job. It would involve re-structuring the current script you use to generate thumbnails to make it support Timthumb, probably more depending how well you wanted it integrated.