The whole of my qualifier from a few years back;
the top of the main track in practice:
Glad I’ve done it, not sure I’d do it again? One to have done for sure though, a unique experience, but there’s better riding elsewhere.
Tips would be: ignore all the “mega bike” crap, ride what you’ve got. A DH bike is fine, and XCish bike is fine. Bike only matters if you can win it…and you’d not be asking if you thought you could.
CO2 (but don’t fly with the cartridges!) inflating a big tyre at 3000m with a mini pump aint happening fast.
If you’ve not got a good gridding, don’t worry about practising the tech singletrack too much, you’ll be in a queue. Practice the start/shortcuts off the main line instead.