Lot's of questions, no problem
Let me take the tool and die question first. Will this help you become a gunsmith, No, but it will make you a better gunsmith when it comes to making parts and tools and you will certainly have knowledge of how things work in reverse which will very useful. I would even suggest that you become a tool and die man and go to work when you have the degree. While in school, take courses in machine shop and welding if your school has that available. A 2yr college or junior college may be the first school I would go to and see if they offer a program for machine shop and welding because these will certainly be needed when working.
The next question is whether most smiths think it is worth pursuing. That is up to you as with all jobs. Don't go into it mislead though. Some smiths have a hard time getting away from their work and some have a hard time getting work. A lot of smiths that don't take business courses have run their businesses into bankruptcy. I might suggest that you specialize in one particualr part of smithing that you like and concentrate on that like rebarreling.
You can get a business liscense and do this part time if that is the way you want to do it. I might suggest to you that you become certified by a school and get your FFL and start out advertising in the gun shops with business cards. Offer a free gun cleaning to anyone that brings you the card. You will get a lot of folks that come in for the cleaning that will end up needing some other work done and you will get to see folks face to face and they will see the quality of your work. A lot of folks frown at this because you will be doing a good bit of free work. Don't look at it that way, look at it as an investment that will get folks to return to you later on because they got to meet you and you did a good job.
If you want just a quick course in gunsmithing that will get you certified, check out AGI. Here's a link for you to look at:
http://www.americangunsmith.com/view.php?id=97
It will be a pretty good course that you can take and go right to working on guns while watching the video. Now, it's not going to give you everything you need to know and you will learn things as you go and as you do more work. I think this course is designed to give a man the basis to work in a gun store or begin to work in a shop on his on. They have more advanced classes available that in California gives you a college level certification because it is taught by retired instructor from Lassen College.
The tool and die work could be your main job and then you could have the gunsmithing business on the side. The two could go hand in hand and provide you with years of enjoyment. Good luck with it.