I come from a background of shooting and editing SD and have never had to directly work with HD. But in craigslist ads I always see people clarifying that they want someone who CAN edit HD. What are the requirements? I have FCP 6 and a 2.66 GHz intel core 2 duo iMac with 4 gigs of memory. Can I edit HD?

I am going to be renting a Sony HVR-V1U (which I have never used before) to shoot with and then will be editing this footage on my mac. I guess my questions are will I be able to do this? will editing from my lacie drive over firewire 800 work? anything else I need to know? thanks for your help

Yes. You can edit a HD or specifically HDV (Sony Cam) with your version of FCP.
You'll be capturing the content via firewire onto you iMac (to your Lacie drive).
These forums have detailed information but under the subheading Non-Linear Editing on the Mac.

Hope this helps,
-C