Hi there,
I would recommend booking a tour as it would be by far your best option, as you only have a week in
Montana. You could also get an
all-inclusive tour of Montana which would include meals, accommodation, etc. and would actually work out better for you.
Another exciting
thing to do is to bus tour the
Glacier National Park with its pristine and inspirational mountain
views. You can also find great
hotels in Glacier Park so need to worry about accommodation here neither.
However, if you feel adventurous and would like to do your own exploring, then
car rental would be ideal as you would be able to visit any areas and plan your own itinerary. In which case I would consider renting a 4x4 over a smaller car as it would come handy, specially if you are heading to the mountains.
Hope this helps
VacationBuddy