It's been 25+ years since I did the AoMM, but I do remember the statement at the start; "This is not a race". Then when I got to the end I found out that they recognized the first finishers!
On the topic of the bike, you can ride a CF bike. I'm a bit heavier than you and have over 2500 miles on my 2010 Specialized Roubaix. IIRC, Specialized says that their CF frames have a MFG limit of 240 lbs including rider, clothing, etc.
I would think that you need to look at your riding and figure out what your drivetrain should be. Are you comfortable with the climbing AND the gear selections that a compact double would provide, or do you really need that triple/granny gear?
Another thing I would emphasize is what a couple of others have mentioned...get that new bike in time to get it completely dialed in for your ride. Believe me, you don't want to find out on mile 65 that your saddle has suddenly become uncomfortable, or that you've complete run out of comfortable hand positions <grin>.
Whatever way you go, you're in for a great experience...
Edited to add:
Stapfam mentions good wheels. I'll echo this. Within a month of getting my Roubaix, I bought a pair of Spinergy Xaero Lite wheels. This was a very good use of $450. The wheels are light and I can really feel how much easier they spin up (or at least I think I can). If it's all in my head, at least it's still there after 8 months...
There are a lot of good wheelsets out there...and whatever bike you end up getting may have a great one. Just don't hesitate to consider upgrading them. You can always use the originals for foul weather...