I am 35, about 30lbs overweight and had a successful VBAC in June. DD#2 was a full pound lighter than DD#1. Yes, you may be statistically less likely to suceed (like 60% instead of 67%, or whatever). Just remember, there's no way to predict how any birth in particular will go. And honestly, I was perfectly happy with 50% odds. That's really not that bad.
My midwife has an extremely high VBAC success rate, because her patients are dedicated to success and so is she. I think that's more important then any statistic.