Need advice on buying a used Hamilton Khaki King

Recently saw the khaki field king in a store and thought it looked really nice. But it's out of my price range.

I see folks selling used ones for around 15-25% cheaper with box and papers.

Questions:

• Any risk of getting a really bad watch? What should I look out for?
• I heard Hamilton servicing is expensive? Upwards of 200 USD? That's a bit steep for me.