1) Prospect list availability is listed on your ML team schedule. You should get in the habit for checking your schedule periodically to look for upcoming events, such as the draft, trade deadline, setting your playoff rosters, roster expansion, etc. so that you don't find yourself caught by surprise about anything.
2) The prospect lists become available at around game 40 or so. I look forward to the draft every year, so I know when we get close to game 40 I'm already starting to think about it.
Still, an inbox notification is a good idea.