soccer ...PLEASE HELP!

[limon]

i run a small book +/- 20 punters. i have the chance to triple that if i take soccer bets from a large mexican contingent i just had chance to meet. problem is i cant make heads nor tails of the mexican soccer league and their playoff system. i have a big group of bettors who want a number on "chivas to advance" i cant find it anywhere. i see at betcris that chivas is +170 dog to win their next game against america. i deduced that the advance part is some sort of addition of the goals scored in a 2 game home and home series (am i right?) but what would the "to advance" line be? my guess is somewhere around -110...PLEASE HELP!