i would refrain from handling, as slowhite mentioned.
However, i dont see any harm in offering food as you would regularly. My kings will eat any time, all the time, regardless of whether they are about to shed etc. Just dont be perturbed if he doesn't want to eat.
I have never purchased an animal from the internet, but have had very good experiences buying from expos/shows. However, you have to be a smart shopper.
I dont buy from booths with dozens of species, but only one or two of each (they rarely have had the animals for very long, and often dont know much about its history). I also ask about the animals feed history, shed history, the parents, and its gender, as well as age.
I tend to buy juvenile, CBB animals only. I wont buy from booths that have obviously sick animals (almost every expo has some booths with half dead veiled chameleons that are way overpriced

).
Those are just my personal 'rules', but overall i've found expos to be meccas of really knowledgable people looking to educate and share their passions