The Yukon, eh? A classic trip by any definition.
A good starting point is one of the more popular guide books, great for general planning, background info on the trip, gear requirements etc. You can supplement with some of the suggested historical books that tell the story of the river and the people.
Like any adventure, a shakedown trip of shorter duration will let you refine your gear list and practice a bit. If you have the time, there are some great trips here in B.C. that would allow you to do that, and in a wilderness setting which is one very important aspect of the trip.
I've got a canoe you can borrow for practice or for the trip. There are a couple of large lakes and rivers nearby that would allow for multi day or multi week trips.
Check out some of the options for canoe types. Most commonly you'll see tandem canoes out on the lakes and rivers. Good handling, plenty of storage required for all the gear, and light enough that a single person can carry if portaging is required.
Clipper Canoes - Home
The wilderness skills are harder to prep for and are usually only acquired through experience. It is by no means impossible, but wilderness camping has it's own challenges that need to planned for. The more a person does it, the better they get and the more enjoyable it is. It's not to be underestimated.
Oh and the mosquitos can be the size of eagles, bring plenty of deet