From what I hear, it's pretty easy to get out to the park where you can do as big of a walk or small, depending on what you'd like.
I find the shuttles from the cruise ships, tend to be a tad short. In Mexico, we were able to take a different bus back (assuming there were different times available), but had to ask.
You could take a peek at the link, this is from the National Park system, it gives you some ideas of how to get out there, and once out there, what all you can do.
https://www.fs.usda.gov/detail/tongass/about-forest/offices/?cid=fseprd495443