The trick with snow and sun is to very carefully monitor your histogram and highlights display. I don't use matrix, rather I prefer spot metering and meter the brightest patches directly and, if I wish to preserve detail there, set them to ~+1 1/3 or +1 2/3 in the viewfinder display. If I don't care about snow detail, and wish to favor a mid-tone subject, I will meter that to 0, perhaps changing to Center Weighting (8 mm). With the tripod, of course, you will be able to shoot brackets for HDR. Where matrix can really let down is in gloomy conditions that lack contrast (think snowfield under an overcast sky).
Handled right, the D300 should be a stellar performer in these conditions even in the long twilight that passes for night in the far north at that time of year. I remember from an early June trip to Alaska that the long, slow sunsets and sunrises can be especially beautiful.