Hi Jodi - Let’s see… the best advice I can give you is to give yourself plenty of time and relax…. if you’re short on time of super stressed out you’ll just get more and more frazzled. Checkout the wedding cake section on Rose’s blog: http://www.realbakingwithrose.com/questions_and_answers/cake_questions/wedding/ There’s a lot of helpful info to be found there.
Also, if you’re making any of Rose’s buttercream recipes to fill or cover the cake with, by all means make them now and follow her storage instructions in The Cake Bible (you’ll probably use more buttercream that you think… I always make an extra batch of BC - leftovers freeze well). The cake layers can be baked now too, then wrap well (vacuum if possible), and frozen to keep them as fresh as possible - they thaw quickly and you can start assembling the cake while they’re still frozen.
Best of luck to you and don’t hesitate to ask all the questions you need to - lots of great people on here who can help you!!!