Congratulations! You will love your 350e! My dealer recommended Madeira polyneon thread. I buy it from sewphisticatedstitcher.com - their prices seem to be the best I've seen for the thread. And if you buy 48 spools of thread, you get a nice storage case free. (I am in no way affiliated with them; just a satisfied customer.)
I love Embroidery Library; their designs are wonderful. And they frequently have specials and sales. I also like designsbysick.com - I got a one-year membership for half-price, and can download as many designs as I want during that time. That's a good deal.
I also bought the Digitizer Jr. software, but haven't yet figured out how to use it. If you unlock the secrets for using it, please share!