hi all the best for your lessons.
would advise you get the tough ones out of the way first. Nav and Technical, i would advise because the Nav skills you'll learn will help with your training anyway.
with regards to headsets a decent set will let you concentrate so much better during lessons. I have allways used Dave Clarke 13.4's. They are reliable, robust, comfortable for up to 2.5 hours and not madly expensive.
all the best
J