Is the .40 pistol NIB? New in box?
It may be a CPO(certified pre owned). SIG Sauer takes used firearms, reconditions them then sells them as CPO. It should be okay.
To replace the barrel magazines, springs & maybe the sights are all that would be required with a SIG P226 series(if the pistol even needs it). I like the R or 1913 rail format for white lights/laser systems.
Bruce Gray of Gray Guns is widely known for top level custom SIG work.