Harri. just run at the paces you have been training at and you will be fine. Take on fluids before and during the race. majority of people who collapse havent done the training or made daft mistakes on race day either going much faster than they trained at or not taking on fluids.
definately spikes. have a look at the front end of your next xc race and see if they are in spikes or trainers with big grip. its different if there are lots of stoney paths to run on etc but most xc i run on are muddy and for that i want light weight with 6 great big spikes sticking out getting me some grip.