Sorry to hear about the broken part. S&W will take care of that for you under warranty, I'm sure. I can't recall seeing others complain about that before, but anything man-made can break. Hopefully they will get your gun back to you quickly.
As to the printing left, if you are not used to the M&P trigger, you might try dry-firing the gun while carefully watching your sights. The trigger can take a little different technique. At least it did for me. I had to teach myself to be careful not to "finesse" the trigger like I might get away with on a 1911 or a revolver, but rather to be very deliberate with it. Try pressing it straight through its release without any hesitation while keeping a very firm hold on the gun (more so than you might consider normal).
I did not adjust the sights on my M&P .45 until I had satisfied myself by observing the sights during dry-firing. The problem was mine, not adjustment of the sights. Check into it and see what is happening when your trigger breaks.
