Ok, I'll bite...
Headrests are the only straight swap

Rest will need a newer Omega, ideally early facelift non dbw manual V6. This is because you need the front door looms and airbag triggers; complete vehicle body loom; airbag ecu, airbag loom, seatbelt pretensioners with seat loom, side airbags with covers, seat back frame and loom (fitting complete seats is best way of tackling seats, but good luck getting the trim to match and you'll need rears and doorcards too); dashboard including passenger airbag, airbag mounting structure and loom; ABS ecu, pump and complete loom; dash loom and TC switch.
That's about it, but you'll be converting the interior to facelift in the process of rewiring it/swapping components...
In a nutshell buy that car and shut up, or buy a late facelift knowing that it's the 'safest' Omega. But we/I told you all this when you first asked (not that you've listened. Note, listening is different to hearing

).