One of the best things about getting a used SIG is that Sig will service it for $129. For that, they:
• Detail strip entire firearm, inspecting critical components
• Replace most commonly worn springs
• Install new night sights
• Lubricate, reassemble, and function check
• Return in factory lockable box (if needed)
• P230/P232 models excluded
I haven't bothered to take advantage of this, simply because mine works so well as is. I probably should -- it seems like a heck of a deal, when you consider you get night sights.