French knives are beautiful, are they not?  You will get the best answers to your questions from our friends in France, but they may still be asleep, as it's 5:30 a.m. in Paris right now!  I, too, grew up being familiar with mostly American  knives, but I have seen a lot of magnificent cutlery on BladeForums from all over the world: Spain, England, Japan, France, etc.
I will take a stab at answering some of your questions as best I can.
1.  I am not sure how to explain how to pronounce "Laguiole" in writing, but may I suggest watching some videos?  You can "Google" "Laguiole" and find many videos on this knife.
2. Traditionally they are slipjoints, but you can get locking knives.  Fontenille-Pataud, for example, makes both kinds.
3. Good brands:  I am very happy with my Honoré Durand knife.  Fontenille-Pataud is well known as a good but expensive brand.  Others I have seen a lot are Forge de Laguiole, Laguiole en Aubrac, Arbalète G. David, etc.  There are many, and individuals too.  
@Âchillepattada  and 
			 Jolipapa
 
		 Jolipapa
 can give you better answers.
4. I am not sure how much I can say here because the forum guidelines don't allow talk of buying and selling in this subforum.  If you were a paid member I could send you a private message. Or if you post your email address on my profile, I could email you.
5.  Traditionally the knives are carbon, but most today I think come in stainless. Some makers give you a choice.  You can even get some in Damascus steel.
6.  I can only guess about this one.  I will guess the Laguiole is not common in Cajun country, being a French regional knife that is about 200 years old.  But I am just guessing, being from south Texas! 
