Lessons for sure are a good idea. Always. I've been riding non-stop since I was 2 years old (I am now 26) and while I never had lessons growing up (we just rode!) I have been taking lessons here and there the last few years. It's amazing what a second pair of eyes can point out and what a more experienced and specialized person can teach you. The day you think a trainer can't help you or can't teach you, is the day you should never be allowed around horses again.
On top of the lessons, I think it would be a wise decision to purchase an older, been-there-done-that horse. You didn't say how old Jazz is, but the other two at 6 yrs old and especially the 3 yr old, they are green horses. While in rarity they can be, young green horses are NOT confidence builders. I would look for a horse that is at least 8 years old (minimum). And if you aren't confident to buy one on your own (I agree ... some people will say anything to make a sale), you can take your trainer with you (remembeR? That one your going to take lessons with?) to help you pick out a horse. Or they may know of one that would suit you.
Either way, I think both lessons and getting an older bombproof horse will be the best thing to build your confidence and get back in the horse world.
∞•*˚ Βгįťţαňγ ˚*•∞
It is not enough to know how to ride; one must know how to fall.