Welcome to the forum.
I would think the best approach would be to look at the service history of your car (if any) and then have a good look at the car.
If you have a look on the forum general help section and also in the maintenance guides then you will see the areas that give trouble on the Omega V6.
If money is no object you could for example include front wishbones, drop links, rear subframe bushes, oil cooler, DIS pack, crank and cam sensors.
However if money is an issue, then it might be best to come up with a to do list.
e.g. clean breathers, Opel oil change and filter. Cambelt and water pump (unless it was done at the last cambelt change).
Where I live Opel dealers are all quite some distance away and never have the parts you need available as V6 omegas aren't common here. I find that there are plenty of suppliers in the UK prepared to ship abroad.
www.ebay.co.uk is a good source. Again if you look at the postings on the forum and in the maintenance guides you will see what items are recommended as only Opel dealer purchase (brake discs for e.g.) and what are acceptable as pattern parts.
With the current rate of exchange UK pound to other currencies it might just work out cheaper getting stuff from an Opel dealer somewhere on the African continent!
hope that helps
varche