Parts interchange

I'm working on my wifes car a 1998 olds intrigue with 185000 miles and a 3.8 V6. It has a cracked head and I am looking for another set to put on it. I have a friend with a 3.8 from an 89 Buick Lesabre I believe, anyway it was an 89 buick that the engine came from. I am trying to find out if these heads will interchange or not. If they will is there anything I will need to do to them. And if not I need to know what will so I can go find the right ones. If nothing else is there somewhere I can go to find this information? This car is still in good shape so I'm really trying to save it from the scrap yard! Any help and advice is greatly appreciated.