Cleaning and lubing is as easy as with any gun. I have one just like yours (without the rail). I don't do anything special. Remove the slide and take the barrel out. Clean everything, lube the barrel and rails and back together it goes.
You picked a good pistol. It will give you a lifetime of good shooting if you take care of it. As to other stuff to put on it. Sites can be changes (night sites added) and maybe a set of those nice wooden grips. Man a Sig looks nice with wood grips..Well..To me it does anyway