Boiled cider kit

Just put on my first batch of cider after doing some 4 batches of beer in my brewing career. I bought a kit can which I might reconsider after reading some posts. My main question is this:
I disregarded the instructions and gently boiled the contents with water for about 15-20 minutes. What kind of problems can this cause?
Also:
After reading some posts I am getting nervous about bottling. Why is it not as simple as beer bottling?
And
I am using a bottle from an office water cooler with a bung and airlock to ferment but the yeast caused bubbling through the airlock. I carefully removed and cleaned this but only after returning home some 48 hours after starting the batch. How bad is this?
Thanks
Andrew(long time reader first time poster)

1. Boiling cider may cause the pectin to set and make the cider very hazy. It can also create a cooked apple flavor.

2. With beer, the yeast will stop fermentation before the beer is completely dry - it doesn't eat up all the sugars. With cider, the yeast will eat all the sugars, leaving the cider bone-dry. If you bottle before the yeast is done, you risk bottle bombs.

3. No problem re: the airlock.