Hey Headbanger,
I had a heck of a time removing the front sight from my new GP100 6" stainless revolver a couple of weeks ago.
I had my son hold the gun and depress the plunger. I took a standard pair of pliers with a cloth over the sight to protect it from marring, and wiggled it slightly while trying to pull up on the rear of the sight. It barely budged, but I did see where the rear of the sight raised itself just barely off of the barrel.
I had my son depress the plunger again and I used a very small flat head screwdriver to slip under the raised portion of the sight and it popped right off. The new Millett went right in with no problems.
They just seem to be very tight coming from the factory these days.
Hope this helps.