How to tie into existing drain under vanity?

I plan to add a second sink to my 63 inch long vanity. I need to tie the second sink into my existing sink's drain. I believe I need to cut a 2 inch hole (or whatever diameter the pipe will be) through a exterior wall stud, and then use a T ABS connector into the drain my existing sink drains into. My question is how do I connect the T pipe into the existing drain? Do I connect it below where the existing sink pipe connects into the drain pipe, and how do I connect it? Are there some kind of sleeves that I need to use?

I also am not sure how to connect the water to the new second sink. Can I use a shutoff valve that has two outlets to it so I can connect two sink valves to it, or do I have to have a seperate shut off valve for each sink faucet assembly?

Thanks,

Jon C.