The start will be hard. By the first corner, your lungs will be trying to force themselves out your mouth and your quads will have gone numb. Hold that for an hour.
For more sensible advice, ride at least one lap of the course, to get an idea of where the tricky bits are. By tricky, I mean where you have to get off and run up a bank/steps.
Oh, and have a look at youtube to get an idea of dismount and remount.
I’d love to have another crack at cross (did a few races on my MTB last year). It’s ace fun, and all over quite quickly.
Enjoy!