Hi, I had a rather nasty surprise the other day when I looked under our kitchen sink. (see attached photo). I never really looked under there but this time I saw a lot of discoloration around the piping for the sink, put my finger on it and pushed right through the rusted out portion as seen. We've never had any visible leaking and this sink and piping was installed 7 years ago as part of a partial kitchen reno, so something must have been done incorrectly by the plumber, I can't imagine it is due to aging in 7 years. When I run water into the sink everything seems to be draining correctly, there is no obvious leaking but obviously there is some kind of leak or else this wouldn't have happened.
Is the part that is rusted a sleeve of some kind that can easily be replaced, or will the main pipe be suspect as well? Can anyone recommend how I track down the leak? I'm also a little concerned about the discoloration on the white part of the underneath of the sink.
Is this a DIY or do I need to call in a plumber? I'm hoping I won't need to remove the sink as it is set into a huge piece of granite. Thank-you in advance for any assistance!!
Is the part that is rusted a sleeve of some kind that can easily be replaced, or will the main pipe be suspect as well? Can anyone recommend how I track down the leak? I'm also a little concerned about the discoloration on the white part of the underneath of the sink.
Is this a DIY or do I need to call in a plumber? I'm hoping I won't need to remove the sink as it is set into a huge piece of granite. Thank-you in advance for any assistance!! 
