A/the which should I use

Could you have a look at the following sentences and say whether they are correct or not?


A formal letter:

Dear Sir or Madam,

I am writing in connection with your advertisement for the Proficiency Photography course in England that I found in the Daily Telegraph from 23rd March 2012.
I would like to ask about the program of this course and an/the opportunity to receive a certificate for its completion.Can you send it to me?
I am interested in the size of groups and some required experience. I prefer learning in small groups because then I believe I will make some progress.
I would like to know more details about the number of hours of classes during a/the which should I use here? day and the total duration of the course. How often do the lessons take place? How long does the course last?
I am still not sure about two things: What is the price of this course? Where do the lessons take place?
I look forward to your answer.
Yours faithfully,
Yesterday 1:49 pm