Personally, I wouldn't want a trial as much as I'd want the seller to take me on a hunt to see how the dog works for him.

My thoughts exactly. Also, I would want to see the dog hunt ALONE. Many a "me-too" dog can look really good paired up with an independant dog they are used to following.
As far as being advertised as "finished"...what makes this so difficult is that everyone has their own opinion of what that means. I honestly feel that a lot of people (not picking, but especially new-commers to the sport) have never had the chance to hunt behind a TRUE powerhouse, so opinions of "finished" can vary greatly.
There is 3 famous quotes, and agree 110% for all of them