At only 29k miles, it's barely run in. And that 2.2 straight 6 is one of the finest engines ever made (in my opinion). The noise it makes is just sublime (we used to have a Z3 with the 2.2, lovely car, especially with the roof down)

I'd probably not bother getting it done, simply because the fluid in there has had such little use it's probably not worn out, or started to burn up.

Those gearboxes, whilst they do have a bit of a reputation for going wrong, usually do so after 80-100k miles.

On the other hand, with that low mileage, it's going to start to appreciate in another 5 years or so, as so few of them will be left. In which case, spending that money on it now will only help it in the long run.

All depends on you really. If the money is sitting there surplus, then get it done. But if not, then I certainly wouldn't be stressing over it.

ZF's guidance is change at 50-75,000 miles (depending on how hard the box is stressed) or at least every 8 years.