For the 3.0 you will initially need more. You need to get a 2.5 V6 set up to begin with along with a 3.0 engine.
The reason being, the 3.0 was only fitted to the Omega which is RWD. So basically you remove the sump from the 2.5, and all the running gear and swap it over to the 3.0 engine. So in effect you will bin everything from the 3.0 apart from the block and heads.
Once you swap everything from the 2.5 over to the 3.0 engine, you will need a new gearbox as the Z22SE gearbox won't fit. A Turbo F23 5 Speed is ideal. By using this box, you can use your original driveshafts etc. You can use the Vectra V6 management, but you will need to keep the original ECU for some of the dash features of the car.
It's not an easy conversion, but it can and has been done.