This is taken straight from the rules as CONCACAF published them prior to the 2009-2010 Champions League. These rules remained unchanged for this years edition so this is what they will go by if two or more teams are tied on points.
Phase 2: Group Stage
• Greater number of points earned in matches between the teams concerned
• Greater goal difference in matches between the teams concerned
• Greater number of goals scored away from home in matches between
the teams concerned
• Reapply first three criteria if two or more teams are still tied
• Greater goal difference in all group matches
• Greater number of goals scored in group matches
• Greater number of goals scored away in all group Matches
• Drawing of lots
To view the whole document you can download the whole .PDF from the CONCACAF Champions League site
So what does that all mean for Toronto FC then? Well it means that they will have a chance of advancing from the group no matter what happens tonight since even if Dallas wins, Toronto will be able to equal them on 10 points by winning down in Texas. If that does happen then these tie breakers will be applied in the order listed. In case you have forgotten FC Dallas won the game in Toronto 1-0, so if the teams do both end up on 10 points it will come down to Toronto bettering that score line.
But what if Dallas can only get a draw tonight you ask. Well in that case any TFC win would do the trick but still only a win would cut it since Dallas would win based on having 1 more point if the teams draw in the last match.
How about if FC Dallas were to lose to Tauro tonight. In that case then Toronto FC still have to win the last game but again it can be by any score. In this case a draw would not be enough because then the teams would end up level on points and the first tie break would go to FC Dallas by virtue of winning the first meeting.
So I hope you have it all figured out now but if you are still confused leave a comment and I will try and explain any scenarios you might have.