The event is on may 21st which should be decent weatherwise,not too cold,nor too hot
I've got a gel seat and will probably also pick up some padded bike pants.
We get a police escort and I don't believe there's a whole ton of bad hills on this run.
I'm looking forward to this for some odd reason
Geekbabe, gel seats are BAD.  They are comfy for a little while, then your butt muscles end up moving the gel around and you will die a horrific death after 20 miles.  Get something like 
this and break it in good.
Do not skimp on cycling shorts.  Expect to spend at least 50-100 bucks for good ones.
Get a 
camelbak or some other backpack drinking system.  Much better than reaching down to grab a bottle.
Do you have clipless pedals and cycling shoes?  Those really help with power transfer.
Other than that, ride, ride, and ride some more.