It's impossible to know what really affected your first labor without knowing exactly the circumstances. Were you in a hospital or at home? Were you induced or augmented? Did you have an epidural? What positions did you labor in, and did you change positions frequently? What kind of support did you have? There are a LOT of factors. The absolute best way to increase your chances of a VBAC: avoid the negative factors by being at home! A skilled and attentive midwife can provide the perfect support for a home VBAC, and give you a MUCH better chance of success than being in a hospital.
For me, I'd never listen to "chances," as there's no way I'd ever schedule a section. I know the circumstances regarding my first birth, and know that had it been handled better, I wouldn't have had a cesarean in the first place. I know that the baby's position also played a big role (he was asynclitic, recognized by my MW immediately when I described my labor pattern). So I planned a homebirth from the get-go the second time, found a wonderful, supportive MW with LOTS of VBAC experience, and prepared for birth. My birth was loooong again, like my first. But with the addition of the midwife, the change of scenery to home, the help of a chiropractor, and the PATIENCE of everyone, I successfully birthed my baby! We all know that if I'd been in a hospital, I would've been sectioned again because my labor took so long.
My main advice to you is to look at the factors. What really happened the first time? What things can you do differently this time? Under what circumstances can you change things? Who and what will be the most helpful to you at this time? Look at all of these things, and ask all of the questions. Ask your MW about her reasonings. As HER what she thinks went "wrong" last time - not just about how far you got, but what you could've done (and can do next time) to change it.
Above all, don't just schedule the section, and don't rely on u/s readings to tell you how big the baby is. If you're eating a reasonable diet (don't be eating junk food and sugars), your baby will NOT grow too big. Besides, baby fat is squishy! It WILL come out!
You can do it, mama!!