What does it take to swap out the 3.0 to the CV6 V8 sport 4.2L

Lots and lots of money, fabrication skill and willing to live without many features the car came with unless you have more money and fabrication skills. Seriously no one will be able to answer this question exactly but I can tell you that swaps are very expensive especially when talking about one that no one does. Buy a car with a V8 and sell the Catera. No other feasible way to do it. Alex