I'm with everyone else, ride what you can and enjoy the experience. If you're comfortable, you can ride in the aero tuck with your forearms on the bars. Keep in mind it's a precarious position. You're much safer in the drops. Another option is one hand in the drops or on the hoods, and the other hand by the stem tucked in. I find the latter to be a good compromise when I'm pulling the group into a good wind or bombing down a hill.
Shaving your legs won't make you any faster (I guess this depends on how much hair you have...) but it will gain you the respect of a bunch of men who wear spandex and shave their legs too. Bike drag and body drag are the two biggest factors, with body being the biggest. Slamming the front and bringing your seat forward (with the requisite raising of the saddle as you move it forward) will help tremendously (this keeps you hip angle open), but at some point you start to lose power. Remember, you're going to be in this position for about an hour so you need to be comfortable. Also, narrowing your shoulders and 'turtling' your head can help a good deal. All of this is free speed, but you'll need to practice the position. Taping the helmet was also mentioned, which can help.
You may be able to use deep-section rims, at least 40-45mm. If you have the option, find out if they are legal.
I'm not the most experienced racer (lowly cat 5), but I do a lot of triathlons and have several TT's under my belt. When I started tris, I used a road bike with clip-ons and competed pretty well in this set-up. I've since moved on to the TT equipment some of the others are making fun of...
Good luck! Remember to have fun most of all, and if you don't feel like puking at the end you didn't have enough fun.