Umm, I've heard many times that Kimber sights were difficult to replace but I've replaced factory sights on three Kimber's that I've owned with no problems. But it's also important to remember that after market sights often have a little extra material left on them so that you can file or mill off just enough to make a secure fit. That means you often can't just pop new sights out of the package and bash them on to a gun with a hammer.
Just my $0.02
Edit to add: FWIW, I really like Heinie Straight 8, Slant Pro sights and that's what's currently on my remaining Kimber. The other setup I found that I like is a single tritium dot up front with a plain black rear, preferably a Novak or Heinie.
