Ok, that's good to hear. It's a very sticky situation, since the breeder would have probably culled the rabbit if you had returned her, but that breeder is very irresponsible for selling a sick rabbit. I'm glad he/she's doing a lot better today. How is it eating? Is it drinking, pooping? I'd still keep it on a hay, water, and pedialyte diet only until normal cocoa puff poops are found.
The cost of an office visit here is $25, and an annual exam is $35. Medicines are $10-15 each, and you'd probably need several. Emergency vet visits here start at $70 for coming in the door. In my area we actually have very reasonable prices compared to the rest of the country. I do recommend getting the rabbit to a vet soon to make sure everything is ok, get some basic info on gender, etc. It's good to have your rabbit seen by a vet annually.
A butt bath can help with the dirt, you may want to put straw down on any puddles.
Edit: I want to stress that until she has round, brown poops, she's not out of the woods, and may still need vet care. Diarrhea in young bunnies can be caused by a number of factors, including stress, poor husbandry, viruses, and bad diet, but they always lead to an overgrowth of the bad bacteria in the intestines, such as clostridium. These bacteria release toxins into the body of the rabbit that make it feel sick. Vets have drugs to neutralize these toxins, including Questran and Bio-Sponge, plus antibiotics that can help re-balance the bacterial population, like Flagyl which angieluv already mentioned. At the very least, a probiotic is needed to help re-balance the GI bacteria. Critical care is found at pet stores, probios is found at feed stores, and even human acidophilus capsules can be given--just cut open the capsule and sprinkle the powder on her food or dissolve in water and give orally via syringe. Do not give yogurt as the lactose in it can cause further digestive upset.
