Go to him, explain to him that you have another offer (make sure you do before taking any steps), let him know how much you appreciate him and how much you've enjoyed working with her and tell her that you'll love to keep her friendship. Give him about 15 to 30 days notice, and pack your bag! If he cares about you, he'll l be happy that you're building a career.

It depends, do you want to be nice about it or not? ^_^ Also, here in America, if you tell your boss that you are leaving your job before you find another job, they might let you go before you can start your new job. Usually you would wait until you have another job with a starting date and then give your employer your 2 weeks notice. "I am currently looking to change careers, so please keep this in mind as i may be leaving this company soon." (Makes them feel like you are not leaving your job because there is a problem but because you are looking for something different)