You definitely have some legitimate concerns. I have a dog with liver disease (MVD) and my dog has had a lot of digestive problems also. He was diagnosed with clostridium overgrowth last summer. Our specialist said that his digestive problems were exacerbated because he has MVD. It is an ongoing battle to keep all his health problems under control and monitor him for symptoms and changes. We have spent a lot of time and money at the vet in the past year.
Diet will be very important for your pup if he does have liver problems. I would really suggest you check out the yahoo group for liver shunts and MVD
here. They have a lot of information there that will be helpful. The UT website
here has some good information.
What were the bile acid number at? If they are high and your dog is showing these symptoms, I would just go ahead and get a referral to a specialist and not waste more money at my regular vet. If it is a shunt, they will only be able to diagnose it for sure with scintigraphy. If a shunt is found, surgery to repair the shunt will be very possibly needed.
Does your breeder have a health guarantee? This is a genetic condition in the breed and they should help with costs.