Broken Fridge, Freezer covered in frost?

A couple of weeks ago, there appeared to be a build up of water in our fridge. I thought it was due to a faulty seal on the fridge door (it is a fairly old model). About a week ago i began to notice that the freezer became increasingly cold and covered in snow-like frost. Now the fridge has stopped working and I am unable to hear the fan running. Any suggestions on what is wrong with it and whether or not I can fix it without a repairman?
Thank you