positive margin/tumor spillage in robotic asst partial nephrectomy

Should I be concerned?  My doctor preformed a robotic assisted lap. partial nephrectomy on my left kidney 4/1/09 removing a 2 cm tumor.  I was in surgery for 6 1/2 hours because the first cut/tumor removal showed there was a postive margin.  The surgeon went back in and removed the remaining part of the tumor (which was confirmed to be clear cell RCC).  Is this the worst case scenario?  Does this happen often?  Everything I've read online seems to say that this is bad, but the studies are very technical, convoluted, and abstracts, not complete.  I am not on any other therapy, I am told to have follow up scans in one year.  Shouldn't I be doing more to ensure survival?