Congrats on the install...
The C-120 needs to have the latest firmware updated btw, if it has been sitting for a year. A new Rev was released just a week or so ago. You'll need to register your unit (don't worry about purchase stuff - its just a formality), in order to access the download. If you also have a the Raymarine 125 (gps unit) it too needs a upgrade as satellite changes last year ..You'll find the Raymarine site fairly comprehensive and they have the full docs for download and troubleshooting FAQs galore.
Operation Docs:
http://raymarine.com/GetFile.aspx?fi...1&categoryId=3
Quick Guide OPs:
http://raymarine.com/GetFile.aspx?fi...5&categoryId=3
Updates Firmware:
Raymarine Marine Electronics - C-Series
Radar OPs with C & E Quick Guide:
http://raymarine.com/GetFile.aspx?fi...3&categoryId=3
The spinning icon for radar, means the C-120 recognizes it is powered on and connected to the unit. Not getting updates could be because the radar is default set to standby mode (default for a virgin display install with radar, and you have to manually change the settings for the scan rate etc,. If you did not follow the calibration after install procedures - I would highly suggest downloading the C-120 manual / radar manual as they have a cheat sheet on the documents pages that can be downloaded to walk you through the basic functions. You'll find them under Products - select the product and then supporting documents.
Beware the power draw of the Radar - and turn it off when not really needed. Not also that the C-120's does not always store your preferred settings, so the routine for enabling radar and changing the intervals it scans etc, will become a normal task.
Hope that helps...