There is absolutely no warranty on the sights from MeproLight (I spoke to them about this) if they came from HK as OEM. HK would have absolutely no liability or obligation to you to replace them either.
However, all of that having been said. . . HK just might toss you a set just to be nice if you approach them in a friendly way and not as someone who thinks HK owes him something. Oh, and one more thing, there is absolutely no way that those sights would be completely dead if they are the ones which were supplied on the pistol with that date code. What is FAR more likely, is that the PD armorer switched out the sights with older, dead ones on the guns they were trading in. . .
As far as needing to replace anything else "just because", probably not. I also live in Raleigh, and I'd be happy to go shooting with you or just to take a look at it if you want me to. I had a USP Compact 45 and a USP Compact 9mm, and now I have a fullsize USP Tactical 45 in Black, one in Desert Tan, and a fullsize stainless USP 45. I am very familiar with your gun, and I would be more than glad to take a look at it with you. Feel free to send me a PM.