I see this is your first post, so welcome to the fold

As for your questions, I'm not sure you should upgrade any parts until after you've ridden the bike a little (sounds like you don't have it yet). Most people upgrade drive-trains because the gearing is not working for them. Again, I would test the current set-up for a while and see what works and what doesn't. You may find that the bike suits your needs in its current condition.