Will this work and would it be easy?

I can't see why that wouldn't work fine. Just don't try using the supercharger. That's a whole different project. I believe the 3.8 you want to use is simply beefed up internally to take the extra horsepower the supercharger creates, but running it in your care naturally aspirated should work fine.

I messed the second part of your question. No, it won't be particularly easy. Changing the engine in a modern front wheel drive car is a significant project. I believe the labor time in a fully equipped shop is around 13 hours. If you're a do it yourselfer working in your garage or driveway with limited tools it will likely take two or three times that amount of time. If the engine in your car is running fine you might be better to give it a good tuneup and some preventative maintenance and try to get another 30,000 out of it. By then the rest of the car will likely be done. Just my two cents worth.

Munron I’m going to replace the motor cause the body is still good on it the engine I was told has a small leak but of what I really don’t know and my wife loves that car I’m just wondering if I could take the engine out and swap in a supercharged of the same year but with lesser miles. I mean I been finding 3.8 on Facebook with like 114,000 miles going for like $500. It just me thinking about swapping the engine to make it last longer

The nice thing about modern cars is that even when they're worn out they still look like new and are often still very comfortable and enjoyable to drive. The down side of that is that one is tempted to pour time and money into something that is on its last legs. At 200,000 mi. you're already living on borrowed time. Lots of then do go 200 and even more but for the most part its a ticking time bomb at this point. It's not just the engine that's getting worn out. Transmission, suspension, and most frustrating of all electrical and electronics are going to suddenly start giving you trouble if they aren't already. Unless you want to do this project just for the love of changing engines, I wouldn't do it. There are lots of low mileage Grand Prixs around that are in beautiful condition that are being practically given away. They're just too old to have any value. If you want to spend money, buy one of those and you're good to go for a long time without all the time and frustration of changing an engine. Again, just my take on it. Feel free to disagree. As for the engine, if you go that route, just use the engine itself. Don't try to use the supercharger. If you do, you'll need to change out all the electronics, the transmission (you need the heavy duty one), the fuel system including the fuel pump and a bunch of other things I haven't thought of. If its a supercharged car you want, and why wouldn't you, then just buy one. There's still a bunch around, and they're cheap and ready to drive. I know because I almost bought another one when mine got wrecked and I found several gorgeous low milers. In the end my wife decided she'd rather have a truck so we bought an Avalanche instead, but even though I have several other fun cars, I do still miss the old GTP at times.