Yeah, keep your inquiries simple and professional and I think you'll be suprised how helpful and friendly music companies can be. I don't think it's exclusive to the business, but it is almost a universal thing within the business, if that makes sense. Make your opening inquiry is simply as to whether or not the manufacturer sells directly to wholesalers, or via distributors; and if the latter, who is the nearest distributor to your area. You don't have to go into a lot of detail about what you're planning, since it's an initial contact. If they sell direct, they may want a TIN, business licence or other info prior to sending you out pricing info.
Distributors tend to be a slightly different animal, but again, keep your inquiries simple and to the point and they will provide you with what you need.
If your plan is to sell exclusively or primarily online, a piece of advice that I might offer you is to build out an affiliate site first -- ie. a relevant content/social site which features ads from Musician's Friend (their program is outstanding and is run through Commission Junction) eBay or another program. Let it run a couple of months before you start making serious inquiries ... as you might imagine, distributors aren't on salaries and need to make the most of their time, and they get a lot of inquiries from people who have decided to sell guitars on eBay like it's the easiest thing in the world to do. So having even a nominal established online presence at least gives the distributor something at which to look and see that you're serious about getting into the business.