It's a great way to earn your first stripes. It is however Full Contact so your machine might get beat up a little.
Loads of experienced builders will attend who will be happy to help out if needed.

Costs are normally 25 pounds, which will get you access to the GSL event as well.
Friday and part of Saturday will be taken up by the qualifier heats after which the machines with the most points advance to the final rounds. There will be whiteboard fights during the final rounds so that the machines that didn't make it can still go and play.