Doug is a very good guy and has a very good business. It will likely be different type of work than at CSMC (restoration/upgrade vs. new construction, respectively) so one thing to consider is what do you want to do. If you like the type of work that they do at Turnbull's, then I would jump at the chance to work for Doug if I were in your position. When you look at his quality of work and the types of guns going through his doors, you will see it is a very short list of businesses that will offer you this oppurtunity.
One thing to consider and ask each potential employer about is non-compete agreements. This may or may not matter to you. At this point in your career, I would focus on working and learning in the areas of my intrests. If that means you may not be able to do that work for 18 months or whatever after you leave a place, so be it.
