Good luck Roger, if you set a goal and start well enough in advance I'm sure you can complete the Vancouver Marathon!
The amount of time you spend training each week depends a lot on your current conditioning and what kind of training load your body can handle, which can vary a lot from person to person. What's your current fitness and training level?
The most important thing when training is to ramp up training load slowly, and listen to your body. It will tell you when you're doing too much, too soon.