Talk to them often; they will learn to talk. If you are gone for a long period, leave a radio on for company.
Toys are essential. They love bright colored hanging toys and swings, bells, ladders, mirrors.
Yes, cockatiels will exist happily with other birds, large and small. They are not aggressive birds. Have fun with your new friend!
Our cockatiels are guaranteed to be healthy when they leave our home. To further insure their good health, we take the precaution of medicating all our birds once a year with preventative antibiotics, a safe guard against parrot fever. We do this annual medication based on our avian vet's recommendation because we do have a great many cockatiels in free flight in our bird room.