He's be at this for awhile the link below is of similar charges some time ago. Wow.
http://www.peninsulaclarion.com/stories/122101/ala_122101ala0050001.shtml
If you hire someone to install it for you, be there while they do it. You'll learn a good deal watching them on this project. Prep before drilling, running wiring, connections, etc. You'll buy a lot more than an install of you're able to watch how they do it.
I made friends with our mechanic...
simple, plug it into the unit and screw it under the dash. Do you already have the transducer or will you be installing it as well? If your installing the ducer is it a shoot thru or a thru hull?