Replace the dragon with a toad, and you get "The Wee Free Men", the first of Pratchett's Tiffany Aching cycle.
The protagonist is Tiffany Aching, a 9 year old girl who lives on a sheep farm. The sheep are not a major plot point, but a lot of Tiffany's life revolves around them. Thinking about the rest of Pratchett's works, I don't recall any books with a significant presence of sheep.
There's a lawyer character also, but he's a toad, not a dragon. More specifically, he's a human lawyer who's been magically turned into a toad. The toad is hardly the only lawyer on Discworld (Mr. Slant the zombie comes to mind).
The sequels to "The Wee Free Men" are "A Hat Full of Sky", "Wintersmith", "I Shall Wear Midnight", and "The Shepherd's Crown". Those take place (mostly) in the same setting, and toad the lawyer is featured in those, too.