Etrefal is right about the ferry, Sherre
There is no ferry from Skagway to Anchorage, ever........In the summer you can ferry Skagway to Juneau, change ferries and continue over to Whittier (a couple hours drive south of Anchorage).......that cross sound ferry route from Juneau to Whittier only runs a couple days a week during the summer and the trip takes about 3 days......it does NOT run that route during the winter.........
You would need to make other arrangements to get to Anchorage, maybe ferry to Juneau or even further to Sitka and then fly to Anchorage from one of those towns......Alaska Air is the only air service.......
The drive from Whitehorse to Anchorage would take a minimum of 14 hours if the weather cooperates, but I sure wouldn't try that in December.......
Why do you want to go to Anchorage ?......If it is only to return to Vancouver, Alaska Airlines also flies south to Seattle from Juneau, Sitka and Ketchikan and you could transfer from SeaTac to Vancouver.......
The ferry also has a weekly route south ending up in either Bellingham Washington or Prince Rupert British Columbia.......maybe you could to find connections from either of those to Vancouver........
Here is the ferry schedule that should give you some more information....
http://www.dot.state.ak.us/amhs/