Be sure it fits your hand well before you write the check. Some combination of the back strap hump and the spacing of the finger grooves makes the 17 a bit awkward feeling to me. The 19 sits in my hand better, and the 26 best, curled pinky and all.
Nothing wrong with changing the front sight and leaving the rear as is, either, in my opinion. The front sight on my 26 got dinged in short order and was replaced, but the rear sight is still original and doing fine.