Using a road bike?

Uh... everyone I know uses a road bike.  They all dream of the day when they can have an actual "tri" bike, though. 

At my race today, there were a fair number of tri bikes.  Maybe even as high as 10% of the bike there.  There were also a good number of full-suspension mountain bikes.  And pretty much everything in between.

Ride what you have.  And have fun!

As for when to slow down your training, many people here subscribe to the "taper"... where you start cutting back on your workouts a week or so out.  Actually, you "taper off" so that the last couple of days before the race, you're not really training.

Have you checked out the training plans on this site?  If you use the workout blog, you can import the training plan to end on the day of your race, that way the taper will be built in. 

I used a thirty-year-old Schwinn 10-speed for my first few sprint triathlons.  The most important thing is just getting out there.

You'll learn more from actually doing your first race than anything you'll read here.

Good luck! 

Mark