anything else to take?
Patch kit is pointless as by the time you've found the hole you'll have lost so much time. Carry at least 2 tubes and know how to change them quickly and efficiently.
The power link is pointless without a chain tool (your multi tool might have one on it) so you might want a chain tool too.
Disposable gloves are always handy as it stops you hands getting covered in oil and then covering the grips in oil after.
As your mate is getting you some gels I'll assume you don't know how to take them;
http://www.highfive.co.uk/pdf%27s/MTB_RFG_ENGLISH_LR.pdf page 18, basically take them around every 20 mins, if you take them once you've "hit the wall" then it's too late. I'd recommend this as an introduction
http://www.discount-supplements.co.uk/sports-supplements-energy-high-5-race-faster-pack-cycle-mtb-triathlonAs said give you bike a once over before the race, check you tyre pressure too (you might want to adjust this depending on the route and conditions, higher PSI for dry, lower for wet and muddy).
going to take the pads out and clean them tomorrow
You shouldn't clean disc pads and the discs should only be cleaned with a specific disc cleaner.
should i just leave the shock pressure as it is, or put some more in?
Your forks should be set at the correct pressure for your weight, too much and they will have too much rebound, too little and they will sag too much. If they ride well as they are them leave them as they are.
