I'll jump on board here and say that getting your various providers coordinated is crucial. Sounds like you definitely need a personal trainer and a nutritionist (preferably who coordinate with each other).
However, when shopping around for a personal trainer, I feel it is lees important that he/she have more knowledge than you, but rather that they can develop a strong relationship with you.
you need someone that you respect. Someone who respects you. Someone whose opinion you care about...that will motivate you to work. their respect for you will makes sure they keep your best interests in m,ind as they help you with this transformation.
i got myself a trainer a little over a year ago. he's attached to my PCP's office as well as my chiro. I came in knowing a lot about lifting...but he taught me some new stuff (kettlebells)...more importantly, we've become friends. I see him once a wekk...he kicks my butt, he motivates me to keep doing what I'm doing. If I slack off, he tells me so. when I do good, he praises me. I care about what he thinks. As a result, I'm stronger and fitter now than i was a year ago. heck, I'm in better shape in my late 30's than I was in my 20's.
Bottom line, shop around, don't settle. But if you come across someone who you like, don't pass them up because they're younger, less experienced MA-wise or whatever...give 'em a shot and see if that crucial therapeutic relationship develops.
Peace,
Erik