adybug, welcome to the forum. Hope you enjoy it here.
Don't forget to check out the Rev forum for some of your questions. Baloo might have some info on folks in your area ... he lives cross country from you. Getting some one-on-one help is the fastest way to learn with Revs.
Yep, trees will make flying more difficult. Theoretically, you need to be ten times the height of the trees away from them to get clean air. Ane, three times the height of any trees in front of you. In practice you don't need quite that amount, but you still need a good run of clear land to obtain smooth air.
If you can fly on 40 foot lines, you'll have no trouble flying on longer lines. With longer lines, the wind widow gets bigger, the kite speeds are reduced, and the brain has more time to think. Group flying calls for 120 foot lines as a standard length. Your local club/group will probably have a standard length of lines for small group flying ... generally in the 75 or 80 foot range. Check around before buying another set.
Cheers,
Tom