"I will be 29 if I go back to school next fall."
You will be 29 regardless.

. Please take this in a lighter vein.
Buddy, 29 is just 2 years more than the average First year MBA student's age. Besides age should never be a factor to question career change. Typically most big stories donot need more than 10 years to occur. You have a lot of time on your hands. Kirk Kerkorian is around 85 and he is still thinking of taking GM management on.
You just need to want it bad.
The only problem with being more than 30 years is that you need to have three years worth of progressive achievement in all areas profession, EQ, maturity, community work etc.
Read what MIT Sloan has to say about age on their website.
"Come to us when you are ready"