Given that the teams are fairly equal, though TX would have the slight edge in the game 6 matchup, so we'll say this game goes from a 50/50 shot to a 52/48. Then, with Lee on Saturday we'll just say 55/45 in favor of TX, that would put the overall series odds at ~20% for a NY comeback.
My numbers were estimates, but close enough to work with. You could probably get actual odds to the 2nd decimal point for each game and get the actual numbers. But, if anything, I think I probably fudged a little in NYs favor.