Sketch up is also versatile in that it can be "eaten" by architectural programs like Revit. It's nice when the architect can drop your frame right into their plan, instantly revealing conflicts with window placement etc.

Can't the framer look at what you have and give you an estimate? I really don't see why that should be a problem to get within a close margin quickly. Is the framer trying to rope you in for paid design work without giving any idea on cost?

Most factors like species and finish are a fairly small consideration, assuming you are not considering anything exotic.
For example, on a frame like you have described, the difference in material price between Pine and Oak would probably only run about $1000. I would also add some for extra labor, due to weight etc. But really it is a small change in the overall percentage. The bulk of the cost is always going to be the joinery, which in a simple layout like what you described is going to be pretty evident.