How to fix my samsung le40r88bd,and how much will cost me ?

My telly is 3 years old and abouut 3 days ago turned it on and the picture was a bit crazy so turned it off and on from mains and it came back on a normal picture.

Then today at lunch time I turned it off after my daughter was watching it, it went off as normal then when I returned to watch the telly It came on but only with sound but not picture so I turned it off and on again but it would not turn on instead it just keeps turn itself off and on..And it makes a popping noise too.. Can anyone help???