First, here's a link to the radar dome.
And here is what Garmin says about connections:
boaters can connect a GPS antenna and one remote sensor directly to the MFD, or, with the addition of the GMS™ 10 Network Port Expander, users can connect multiple MFDs and sensors to the same network. Each networked MFD can be configured independently.
Since the new model is not yet out, all I can do is assume that it will work just like their older antenna models and plug directly into the chartplotter port. The chartplotter also includes a GPS mushroom antenna sensor and cable. The radar cable supplied with their other domes is about 40ft. so you may or may not need an extension to that. You will need to buy whatever mast mounting system you choose and assorted minor stuff for the install.
The larger displays are significantly better AND more expensive but I would suggest you take a look in WestMarine or somewhere else and be sure the 5" screen will be sufficient for you.