It might just be that the deck boards need to be replaced and not the whole thing. Do you have pictures?

This is why you hire a home inspecter. That's what you then ask them. No one here will tell you the answer you need. Especially without pictures. Just go get the inspection done, as it sounds like you could use the guidance regardless.

Thanks,
dont have pics sorry... Ill have to ask someone to come look at it and see how deep the damage is.

You may be able to extend the life of the deck by flipping some boards that are rotting on one side and only replacing the worst of the worst. We've done this on two different properties. We squeezed 5 extra years out of our current deck by doing this. Often it is just the top side of the boards that are splintering and the underside and main structure is ok. You won't know until you start pulling boards up (unless you can get a clear view of the underside and substructure).