G'day BR,
I've had no problem with moisture behind the screen in mine...I used it in a 15ft Centre console tinny before graduating it to the Riptide's hard top...so i've not experienced any concern.
As far as adjusting the gain and range, it is via a pop up menu system and making adjustment by hitting the "volume" button...a bit fiddly but can be done...certainly the Furuno with its dial system has greater flexability in this area of function. I have found that the auto function is very sensitive and works well for me even in the shallow. Having said that i am very satisfied with my Raymarine and functions perfectly for the kind of fishing I do...offshore reef stuff.
Once you have adjusted a setting it needs to be readjusted...it does not return to the default when you power down and then power up again.
I'd give Jason at Sundown Marine a call 0732033007. I'm sure you'll find him a wealth of information but if you don't get him today, you'll battle to get him til after the boat show unless you can catch him at the boat show on the Sundown stand
all the best
Rhys