I guess I don't understand what you mean by calibrate. I have the Garmin GDL20 sounder module hooked up to a 2006C with a temp sensor on the transducer. It displays the surface temp just fine, and provides a graph that can be set up for whatever range and time you want. The temp display/graph can be shown on either the sounder page or the map page. But the measurement is simply the temp at the transducer depth with no provision or need to calibrate it. (Of course, there may be something in there like you mean, but I don't use anywhere near all the features it has.)
I have a Raytheon sounder with depth-only display and a thru hull transducer. To my surprise there is absolutely no interference between it and the dual-frequency transducer hooked to the Garmin. I run them both all the time.
I also have a 3210 with the 4kw radar. I don't have the network sounder module because I don't need it, although I could connect the older module if I wanted, but I am content with using the smaller display for the fishfinder. You will not be disappointed with the function and features of the 3210 network. Just make sure you are able to mount it far enough from your eyes. The display is huge. The Radome isn't exactly small, either, but they have come out with a 24" as an alternative to the 28" I have. I think they have open array transmitters now, too.