Well, directions is pretty easy - most people just plug the zumo audio out into the AUX plug in the left pocket. Select AUX on the radio system and you'll get the directions. Aux is separate from Intercom - so both can be on at same time. If want to listen to music, load the zumo with a memory card of songs and good to go.
Phone - diffferent story. Now I use a GL2WAY which can interface with the zumo system using a mic splitter. BIKEMP3 (maker of the GL2Way) also has a MP3 player with a bluetooth system that will work, and I like it. It won't work on bikes with the Nav system, but will with the others (Actually, I have a new one if you're interested. Bought for my old bike, upgraded the bike before it arrived).
J&M also has (or at least did have one) mp3 and bluetooth system - my new bike came with it from the previous owner- kinda glitchy. Prefer the BIKEMP3 stuff personally.
Edsets used to do an interface as I recall - may want to check with them. Also Electrical Connection. This is an area I'll defer to other members on the board who may have different setups. I know RadarWing has a helmet bluetooth system that interfaces so well with his phone that I can't tell he's on the bike.
Now Pete of BIKEMP3 has stated in the past the Garmins (and Zumo's in particular) have an input issue with audio/voice. You can hear okay, but the mic splitters and the Zumo's just don't always like to play well together. Hard for the other person to hear you.
I'll be following this thread and see what the other knowledgable types on the board have to say.
Ordering from Jon is via email only. Ordering directions are clearly outlined on his home page: http://www.cellset.com/
The phone thing is a whole different issue. The best, easiest and most trouble free way is to install a Sena Bluetooth headset in your helmet. Your phone will pair with the 660 and the 660 will pair with the headset. It's seamless and it works.
If you don't what to go the bluetooth route, then there is the mic-splitter that ssncob referred to. It's available from EdSets. Getting that to work is hit and miss. I have it on my bike with a 660 and it works pretty well. Others cannot get it to work at all.