FWIW, let me chime in with a bit more information.
1) Glacier N.P. is open year round. Snowshoeing is very popular in the winter.
2) The campgrounds switch to primitive camping only, on Sept. 22. In practical terms, this means that they shut the water off. Pit toilets are available after that date however. I presume that you have to pack your water in, although it is conceivable that you could get water from the ranger station, but I don't know.
3) the hotels and motor inns within the park close around the same time for the season.
4) Going-to-the-sun road will close based on snowfall, but will typically be open from each side up to a point which varies depending on weather conditions. I don't think it usually closes completely. It will open to through traffic in June most years, again depending on conditions.
5) My family visited earlier this month and I learned that there are about a dozen fewer glaciers in the park than when I was last there in my teens. They expect that all of them will be gone sometime between 2020 and 2030.
6) it is a fantastic place to view wildlife. We saw mt. goats, deer, squirrels, a marmot, ptarmigan, a fox, and when I'm done printing it, I will share a photo or 28 that I shot of a bull moose in the gallery. Yeah, I went a little crazy shooting for nearly an hour while he drank and cooled his hooves in Lake Josephine.
7) there are motels within driving distance of the park where you can find lodging and drive in for the day. Very worthwhile. Check out the webcams.
8) bring a lot of film Wayne, a lot of film