I agree with the previous poster -- relax! You are starting on a wonderful, loving adventure -- Yorkie ownership. Although it is often questioned who owns who.
I would order a good shampoo, conditioner, and brush on line. I have limited shopping nearby too so I order most of my supplies online.
I would recommend one of two brushes: The Madan brush -- a fellow YT member minimoso sells these. Look for her thread on Madan Brushes in the for sale forum. The other choice would be the Chris Christensen brushes. Everyone is raving about the wooden pin brush lately and that is the one I would order if I was going to get another besides the Madan brush. Until you get one of these brushes, you can use an old brush of your own. As a puppy, you are more getting them used to brushing then anything else. So, the brush you use the first couple of weeks is not all important.
For shampoo and condiitoner. I love the Espree products. Others recommend the Chris Chritensen products, Minksheen, and Buddy shampoos. Any quality products will work for you. The exact brand is a personal preference and you may want to try a few. You can ask for free samples of some products. If you used your own shampoo or a cheaper puppy shampoo a few times waiting for a quality product, nothing would be hurt. Over time though, using the wrong products can dry the skin and dull the hair.
Your puppy will be very forgiving if you don't have every single product on hand when he comes home. Just make sure you have the same food the breeder was feeding, (you can change, but only by doing it slowly) a bed, a blanket, an xpen or play yard to confine him when you can not supervise, food and water bowls, some Nutrical (just in case for low blood sugar), puppy pee pads, a carrier, (harness & leash if you are going to need it to take him out), some toys .... and the rest you can accumulate as you go.
You are going to have so much fun!