I have taken the train from Montreal to Halifax, and from Winnipeg to Vancouver. The Montreal-Halifax trip was something like 24 hours, while the Winnipeg-Vancouver trip was a few days. Both were magnificent, and if you put them together, and added the addition 2400 kms between Montreal and Winnipeg, would make for more than a week’s travel
You will see whales in the Gaspé, forests that go on forever, the citadel of Québec where General Wolfe defeated Montcalm and won Canada for Britain, more forests, the Great Lakes, cliffs and rocks like you wouldn’t believe, moose, wolves, and bears, plains where the sky is so big there is nowhere else on land that you will get such horizons, the Rocky Mountains, and finally, Vancouver.
Do it.