I'd second Veronica's suggestion about a nutritionist if you have 100 lbs to lose. You'll be at it for awhile so you need a sensible plan that you will stick with. She/he can give you a good macro nutrient breakdown depending on your activity level. Make sure your YMCA nutritionist has some type of certification.

Your personal trainer should set you up with a full body, compound exercise routine. That means squats, push ups, pull ups (assisted as needed) and not bicep & triceps curls. You want to engage as many muscle groups as possible during a movement. For example, push ups engage pectorals, deltoids, triceps and abs. Leave the single body part movements for the bodybuilders.