As with any breeding, check the health certs on the parents. Don't take anyone's word for anything, ask to see copies of the certificates.
Are the pups on the ground already? If they are it's pretty easy to tell if they are Dudley or not without going through all the genetics "what if's".
I just bred my chocolate bitch to a yellow sire in January. I did a lot of homework before agreeing to the breeding and found that in our particular case, the chance of a true Dudley was very small and I had someone lined up to buy any Dudley's we might have, so I went for it. We ended up with (5) yellow and (4) black. Not a single Dudley in the bunch. I do have 1 yellow female that has a liver nose and one yellow (can't remember if male or female) that has a black nose with a liver spot on it and a single pink pad on one front foot (all other pads are black).
It's her first litter so I have no proof to show that they will turn out to be good hunting dogs, but I also haven't had anyone present me with any proof as to why they wouldn't. I can tell you that they were 5 weeks old Tuesday and are already having a ball carrying duck wings around the back yard, don't flinch when you slam the kennel gate, bang pans, etc...
Coincedentally, my girl is from a Chocolate male / Yellow female breeding.