I'm curious, how much have you seen about Civil 3D? The reason I ask is
that if you haven't really seen much, you may not get too much out of the
trial version. There is SO much to learn it may be difficult for you to
evaluate it in 30 days playing with the software once in a while.
You might consider getting a reseller to come to your office and give you a
demo. This demo will be free. If it's not, find another one. Tell them
what kind of work you do and provide a sample of your data so they can
tailor the demo for you.
After that you can give the trial a run, but it's still going to be a little
painful especially that you're moving from a non-Autodesk product. What I'm
getting at here is don't judge the success, or lack thereof, of the trial
simply by a 30 day experimentation. Ask a lot of questions in the demo and
after the demo, since you'll likely think of far more afterwards.
Good luck.
--
Matt Kolberg
Global CADD Systems - A division of Cansel