Rear sight is in a dovetail, same as GI. At least, it is on my 15 year-old Springfield 1911 A1. If they did something different on your model, I'd be surprised, but you could call and ask? Keep in mind there is a dimple in the slide in the bottom of the dovetail that bears up hard against the sight, so it should be drifted out from left to right and installed from right to left.
The front sight has a soft steel stem that goes down into a square hole in the slide and is crimped, then ground flush with the inside of the slide. If you have the barrel and bushing out of the slide you can see it. You can cut the flare of the crimp away with a Dremel tool, but the sight will no longer have enough metal to reuse, so most people just grab it carefully with pliers and twist back and forth until it breaks off, then push the stem out from the outside with a small drift punch.
Note that the Springfield I have uses a hole that is bigger than GI but smaller than Goldcup size, so you have to get a front sight made for a Springfield slide to replace it (not to mention the crimp tool). If you are going for an after-market front sight with a dovetail, you'll have to get someone with a milling machine to cut the female dovetail into the slide for you. You can get the dovetail cutter from Brownells. If you go to a gunsmith, he should already have one. There are only two standard sizes, IIRC.