I think from a money perspective, it would actually be the other way around. Write the book and get your name out as an expert practitioner of your area of business. A book like that won't be a best-seller since it's so niche, but it will put your name out there and you will be able to say you literally wrote the book on international sales of capital goods. The weekend workshops, on the other hand, you can charge a lot for, or at least you should be able to once you get your name out.
I agree with this but there is nothing wrong with putting together a two-day seminar to get your feet wet and start to build your credentials. The more things you have to put in your bio, the better. The challenge for the seminars will be marketing it in such a way that you get the right people to attend. You could contact one of the sales training organizations, like Miller Heiman, and see if they have any interest as adding this topic to their portfolio of training seminars....but they will probably want proprietary rights to allow other trainers to deliver it. But that may not be a bad thing.
Actually, now that I think of it, I have a contact at ASTD ( http://www.astd.org/ ) that is in Chicago. I will pm you or we can discuss later this month. She should have some good insights into this topic.