Some commands that may help

Suppose you have a file named file.txt which has hunders of lines and you want to see lines 100-120

head -120 file.txt|tail -20

Find and replace text in vi: 1,$s/oldvalue/newvalue/g (or) :%s/oldvalue/newvalue/g

More help with vi here: http://www.ahinc.com/linux101/vi.htm