Ranch dressing mix is salt, pepper, dill weed, onion powder, garlic powder, chives, parsley and buttermilk powder. I would sautee fresh chopped onion and garlic rather than use the powders. I wouldn't put buttermilk powder in a taco soup though and certainly not dill. But if you like it, go ahead of course.
Taco seasoning is generally a combination of salt, onion powder, garlic powder, chili powder, ground cumin and ground coriander. (Some brands of chili powder already have the spices added.) Assuming you've already salted it and used onion and garlic, just add ground chili, cumin and coriander.
Here's a thread that discusses stock making methods. Follow the link posted by Nicko, for a detailed step by step with pictures.
Hard to say how long dried beans would take. Depends on the beans, whether they are pre-soaked and the cooker. I see people reporting ranges anywhere between 3 and 6 hours. I would do it while you're home to keep an eye on it.
I think frozen corn is better than canned. Fresh even better of course. And I don't understand people who insist on cooking it forever. I like it just heated through.