Buy the tools you need to disassemble the Shogun, all the way. If it fastens, remove it. Clean and re-grease, add chain, cables, wheels, tubes and tires. Then determing, upon re-assembly, precisely which major components need replacing. I'd bet brake levers, and not much else, unless it's got a TON of miles.
Total should be well under $300. Knowing now what I didn't know then, this is what I'd do.
And then, after all this, you could bring home any bargain find and have another bike for cheap, and with work, it'd be like new. Good experience.