I agree with everything you said accept,
Not necessarily. You can teach your horse to lunge, without a trainer. Whether you have or haven't lunged a horse before.
The internet is a great place for this kind of thing.
I disagree, if you wish to lunge your horse effectively, then I would suggest getting help from someone with experience. Its a good tool to have in your belt, but done wrong is serisouly ineffective and can make like difficult for when you ride.
As a beginner to lunging, would you know the following
a) What equipment to use on your horse ie halter, bridle, cavesson, lunge girth, bugees, pessoa, side reins, lunge, double lunge.
b) How to effectively send your horse out and away from you at a walk.
c) How to stop your horse immediately if the situation arises.
d) How to slow your horse down in a gait.
e) Where you should position yourself for the horse to move forwards/slow down.
f) If the horse ignores you, what do you do?
g) chat to your mates whilst you're lunging? Answer to that is no!
h) Able to flex a horse on the inside bend effectively without said horse coming in.
The list goes on, but to be an accomplished lunge artist, its best to get someone who knows what they're doing involved.
Oh. And wear gloves!
Sahara, I have always spelt Lunge and lunge, longiert in German, but on every thing English, its labelled 'lunge equipment'.