I flew in on a Sunday and flew out on the next Sunday. First full day, I drove around, mostly looking at railroad subjects. Second and third day, I was in the Yukon. Fourth day, I took the ferry to Haines and rented a car there. Fifth and sixth day, I rode the train twice, drove over to Dyea and the Taiya River, and drove some more around Skagway looking at railroad subjects. Next day, I left.
Every time I have been there, I always leave at least a full day for driving around Skagway looking at railroad subjects. If you're a rail fan, you will want to take time to look at the equipment and take photos.
Some cruise lines used to have an option by which you could skip Juneau, and fly ahead a day before to Skagway, or fly down a day later, depending on which way the cruise is going - north or south. It gave you two days at Skagway. I haven't heard about this recently. I've never taken a cruise. Too many people.
The place I eat at most often is the Station Restaurant, across the street from the grocery store, on 4th Avenue. Their hamburgers are good and so are their halibut sandwiches. A lot of locals eat there.
Robert