The real ones used by physical therapists, chiropractors and athletic therapists are FDA registered therapeutic devices that can legally only be sold to one of these licensed practitioners.
Not true, actually. For instance, they're available from MassageWarehouse.com
A real 1 or 3 Mhz ultrasound in untrained hands is a dangerous device. It is quite easy to damage tissue with an ultrasound.
True.
I suggest you see a physical therapist who will, after a proper assessment and maybe some treatments, recommend to you safe and effective things you can do to treat yourself if you tell them that is your intention.
Absolutely. If you have a dislocated shoulder, the first thing is to get it back in place. And delaying it can actually make the process worse, as your muscles "adjust" to being out of place, makes it more difficult to overcome.
If you have the idea that a heat source of some kind will "fix" a dislocation, you're sadly mistaken. And if you think that spending $1,100 and up for an ultrasonic is less expensive, think again. Because, you'll simply be spending that amount in addition to whatever you spend at a "real" therapist.
And besides, time is money. You'll get back into the swing of things much faster if you see a therapist. As Bob said, a physical therapist would be a good choice. But so would an Osteopath (sort of like a chiropractor, but with a medical degree, a.k.a., "DO"), or a massage therapist trained in Neuro Muscular Therapy ("NMT")