Ill try to answer your questions specifically but I think vroom gave you the basics you need to know
1)I think you should join a gym first, unless you have adequate equipment at home(power rack olympic, weight set, bench) and a person to help you out thats been training for some time. The gym will give you a good environment and be full of people who can give you sound advice if you ask for it. Training at home will obviously give you freedom to workout whenever you want and never have to wait for a bar or rack.
2)A good personal trainer could be very valuable for a beginner but a bad one could start you off on the wrong path. Check some out if you have the extra money but if they dont mention the words squat deadlift or press at any point, run away. This site is a valuable tool for learning and interacting with people but nothing replaces hands on experience with a person showing you what to do.
3) Regardless of your goals you should try adapting your eating habits to Dr Berardi's 7 Habits of Highly Effective Nutrition Programs and then adjust the calories accordingly. Once you can get almost all your meals to be healthy and protien based you will be miles ahead of the average weight trainer
As far as training goes, any workout from here that uses multi joint compound movements will be fine as long as your perform them with proper form. Maybe check out Big Boy Basics by Chad Waterbury, http://www.T-Nation.com/readTopic.do?id=459533
4) As far as general advice, consistency is the key for anyone here, learn to eat for your goals, train hard in the gym a few times a week and be patient, the results will come. Good luck and come back with any additional questions