I have never ridden at ONF before. The family and I will be going up in a couple of weeks. I have a few questions that I have not been able to find the answer to: 1) Do you need a GPS to navigate the trails or are they well marked? 2) I understand that the green registration stickers are required, helmets for anyone under 18, double riding is allowed, have I missed anything that I need to know? Any help would be appreciated.