Need on new business and business plan help!

Hi everyone, I'm starting a new business in my town particularly a Retail/Guided Outfitting Business. my business is in the Hunting, Fly Fishing and Fly tying, fire arms, ammunition, outdoors retail. where I'm located is in the great state of Montana, and there is absolutely no competition whats so ever for at least a 100 miles in either direction, we all ways get people passing through asking if we have a store like the one I'm describing in my town, and sadly we tell them they have to go a 100+ miles either west, south, east or north into Canada. so I'm jumping on the ball and going to provide these services to the locals and tourism people alike not to mention I'm only 20 minutes away from Glacier National Park:cool: but my question is on the business plan, i need help with choosing a good legal structure and whats the best legal structure for a retail business in that field.... any advise or suggestions would help!