Hi Mate,
I was driving a saab today, a spanking-new 2.0 petrol turbo. I hope yours was better than that as the gears and suspension were terrible. I wasn't very impressed after driving my Z, but then i haven't really liked anything much after getting used to my Z
The normally aspirated V6 on a Z is not under any real strain and shoudl be good for far more than 100K, in fact i see no reason why it shouldn't go much higher. I`ve had V6 cars that go up the 1/4 million miles which is why I always like a V6 (that and the great torque curve). Prices are cheap because it is a big engine and petrol and road tax aren't as cheap as they were. I get 30mph from mine, although I do quite a few motorway miles. I do have a bit or a lead foot but it seems to forgive me
As with all cars, FSH and be aware of the common faults for the model, although for an 04 they will most likely have already been fixed under warranty.