I need to remove the barrel and front sight from my upper in order to have the gunsmith thread it; should I attempt this or just let him do it; and what is involved?

the only thing you really need is a barrel wrench and asomething to hold the upper in whilst you wrench on the barrel nut. Id recomend a bench vice and upper reciever block. The wrench and block will cost you around $30 or so depending on what you get and where you get it from. To put it back together, though you'll need a torque wrench as well. Unless you're planning on doing more AR work in the future, I'd just let the smith do it.