to answer your questions craigslist is a place online where ppl can post personal ads for just about anything and then you set up a meeting with them
you should be careful of scams and fraud be very skeptical and if anything looks a tiny bit fishy then move on and like i said make sure you bring someone who is an expert in the field so they can give you an objective opinion
as for the practice i was kind of obsessed so i would pick it up and practiced several times a day in order to speed up the process but if you put in a solid hour each day which is not too hard but you have to be dedicated for like 2 weeks should do the trick but it is different for everybody and im sure your future teacher would tell you it takes a load of patience and concentration on improving your sound or tone so you have to make a firm decision and stick with it through the frustration
i have no experience with clarinet sorry flute was definately more than enough to keep me busy i think its a matter of preference i used to get wierd looks when i told ppl i played the flute but i just loved the sound so i stuck with it
good luck with your decision and if you have any more questions feel free to post and il try to help you out as best i can