http://www.gpnotebook.co.uk/simplepage.cfm?ID=1100611607&linkID=17862&cook=yes
decent enough summary....
hernia's are seen a lot....never seen an umbilical in anyone else other than a woman, so its not that rare either

The repair seems like a relativly straightfoward operation, 1, possibly 2 incisions will be made around the umbilicus, any bowel or omentum (fatty crap that just protects the bowel) will be repositioned to avoid further incarceration (trapping) and to secure the weakness/defect the rectus sheath of the abdominal muscle will be overlapped over the defect (akin to having an electrical cable frayed and the blue and brown wires protuding out, and the surgeon taking part of the blue wire and sewing it across the brown wire so it makes a tight barrier which no wired can come out from...the wires are the abdominal muscles and the blue and brown insulation is the rectus sheath)
sorry if that is a poor explanation...it is hard to explain the blood and guts of it. if you want i can show u on an online gray's anatomy but it will probably confuse me as much as you