The big thing you can do in one month time is ride TT the bike a lot. You need to both get comfortable riding on aero bars for extended periods of time and you have to be able to make power in that position. Both sound simple but aren't that easy. By the time you're 40k is here, you should be comfortable riding in the aero extensions for an hour at a shot if not more.
One thing I always do leading up to long TTs is to do all my long intervals (2x20s or 2x30s) on my TT bike and stay in the aero extensions until done. Out of the 3 hours in a training ride, 2+ will be in that aero position. Do them solo, you don't want to be riding your Cervelo with a group.
You can expect some power loss compared to a normal road position but if you spend enough time preparing you can minimize it (one place a wattage meter comes in really handy).