With an overly hormonal bird, the most important thing to take into consideration with the light is the Ktemp because a high one would put them in breeding condition. I have seen full spectrums that have 6500! I actually like 5000 better than 5500 but it's not easy to find a 5000 ktemp with a good CRI... Another thing about the lights, I usually turn on 'regular' bulbs for a while and then the full spectrum so they are not on all day long because we need to remember that the specs given are what the noon sun light looks like and we don't want noon light all day long, either...
Don't worry about changing his diet slowly because, even if you did not want to go slow, it will still be slow as he/she will take his/her own sweet time to begin eating a large range of produce -switching a parrot is never an easy or fast process BUT, on the other hand and in my personal experience and opinion, few parrots are better eaters than amazons! Mine even eat their greens almost every day (they got broccoli-rabe today which they like very much) and that is something I can't get the grays or the senegals to do often enough to even call it 'regularly'...
Also, don't worry about not been sure of how to cook the grains - birds don't care if they are too soft or too hard, they eat them anyway

But, for a first timer, I would make them harder rather than softer.