1. Kansas City doesn't have much detail in the lore, which makes it sort of a backwater in shadowrunner circles, but leaves it wide open for development in your game. Kansas is the southwest corner of the UCAS, bordering the CAS, Pueblo Corporate Council (PCC), and Sioux Nation, so relations with those neighboring states are pressing concerns, affecting both legal commerce and illegal smuggling. But Kansas City is in the northeast corner of the state, straddling the border with Missouri (in fact, it's mostly on the Missouri side), so those borders are still comfortably remote. Browse Google Images to get a feel for the place, check out the Wikipedia article, then give it some Sixth World flavor. Such as: a trolltown on the waterfront, a dwarf district, a coven of vampires, some transplanted magical faction like a major Buddhist or Qabbalist temple, a notorious local dragon who's an art snob (self-appointed curator of the Nelson-Atkins museum, willing to hire runners to expand his private collection), and so on.
2. Vampires have plenty of info available, starting with the description in the core rules (p.406), then the chapters on Infected in Run Faster ("Into the Night," p.124-143) and Howling Shadows ("Whispers in the Blood," p.77-91).
3. A local corporation can be entirely your creation, and could potentially be very powerful on the local stage while staying below the corporate radar. Remember, there are only ten triple-A megacorps with a seat or two on the Corporate Court; but there are over a hundred double-A megacorps with extraterritoriality; and there are thousands of single-A corps that aren't big enough to call "mega" or claim extraterritoriality, but are still major multinational corporations. Below these, there are countless national (B-rating) and local (C-rating) companies that still have enough clout to own local politicians and form little corporate fiefdoms where they're the big fish in a relatively small pond. When you own the mayor, the sheriff, the district attorney, and a few judges, you can get away with pretty much anything. Maybe there's a construction company that's all mobbed up, or a tech factory that employs over 10% of the city, or a law firm with blackmail files on all the right people, or a pharmaceutical company that secretly operates local clinics as a front for testing new products on the disadvantaged and SINless. Or a chemical factory that uses ghoul workers off the books and bribes inspectors to skip their inspections.
4. Early missions should set the tone for your campaign, and introduce your players to the major locations of the city, major organizations (gangs, crime syndicates, religious groups, political factions, law enforcement, media personalities, sports teams, even popular bands), and major NPCs (some of whom should become contacts if they aren't already). Check out the list of basic shadowruns in the core rulebook ("Run Templates," p.336-338) and run a few examples to give players a feel for the game.