Look in the Sunday paper under the job listings. They will always be listed there. Call the BBB tomorrow morning or look them up online. Here if you call the BBB you say the name of the business and you get a recorded message saying whether or not they have negative information about them and what that info is. I think you can do the same online.
Agency's do pay more because they, by in large, do not offer any benefits. You can schedule any way you want to. No minumum days per month, no weekends if you don't want to work them.
You will be expected to fit in and will be sent to just about every dept a hospital has.
I'm looking forward to doing some agency work once I get some more experience. I've already got my agency picked out. They only staff one particular hospital chain so wherever I go the computer systems, med dispensers, protocols will all be the same.