Don't fret too much. Before you come up, drink lots of water (not Gatorade or sodas), and don't skip a meal. If you normally drink two drinks, drink only one or avoid alcohol the first day you are here. Adjust to Ned altitude before attempting to hike up to 10,000 feet or more. Signs of High Altitude sickness: nausea, dizzyness, severe headache. If you have these sympton after taking all the precautions, get thee to a doctor and lower altitude. Seniors - give yourself a break, keep it slow the first couple of days. The pace is slow anyway.
Nederland has a really high elevation, and some people have a problem adjusting to the altitude. If you start feeling lightheaded and dizzy, you may want to descend to Boulder untill your body adjusts.
Beware the wind! It can get pretty nasty up here and gusts of 80mph aren't that uncommon. No crime. You have a greater chance of being nuzzled by a large dog than a crime being commited against you. And the weather...in the mountains here it is very unpredictabe. It can go from sunny upper 70's (F) to snowy low 30's (F) within a half hour so be prepared for just about anything.