Hi there and welcome to YT. I'm sorry about the loss of your dachsund. I have one, too. They are great dogs, but I understand your concerns about getting another one due to back issues.
There are several parti breeders on this forum, so I'm sure they can answer your questions about the coloring. Until then, here is a link to more info:
http://www.yorkietalk.com/forums/yor...formation.html
First and foremost on finding a good yorkie is you are buying the breeder first, and then the dog. You are going to want someone who will be there for you long after the sale is done. You'll preferably want someone close by, you'll want to meet them in person before you buy the dog and you'll want to see the conditions the dogs are being bred and raised in.
Liver shunts:
If the breeder is clueless about shunts, RUN! If you scroll to the bottom of this screen, you'll see a search bar. Type in liver shunt and toggle the search to yorkietalk and you should be able to pull up a lot of good information. One of the tests you will want to have done is a liver enzymes test at 6 months of age, even if your pup seems perfectly healthy.
Price: It really varies by region and quality. In general, you will pay less over all for a "pet quality" animal- that means one who doesn't fit the AKC showing/breeding standard. The closer to the mythical "perfect dog", the higher the price. Yorkies with a good history of championed ancestors will run you more because they fit that image. Stay away from anyone who is charging more for a "teacup" or smaller than average yorkie- AKC doesn't recognize the teacup label. Smaller than average dogs are also more likely to have health issues over their life time. That being said, anyone selling yorkies for less than the going rate may be cutting corners in their breeding program somewhere.
Health concerns:
Yorkies (and all toy breeds, really) have a higher incidence of hypoglycemia, Legg Calve Perthes disease, subluxated patellas, atlantoaxial instability, gum disease, collapsed trachea and liver shunts. They will do best with a vet who is well versed in the health concerns of the toys, especially anesthesia protocols. Ideally, they shouldn't have multiple vaccines given in one visit, and the vaccine series shouldn't be started at 6 weeks.
I'm sure I probably left something out, but someone else will come on and fill in the blanks. Good luck on your search. Doing your research first will help you immensely in the long run.