A very similar question was asked a couple weeks ago. Take a look here for further perspectives.
Real effects on the health care system and culture & society at large will depend on how many of these devices are available and where they are available. And of course who controls them.
I don't think it's really feasible to place such technology in the hands of laymen. You're still going to need nurses to triage and specialist doctors to diagnose and prescribe treatment and specialised technical nurses to set up the device and administer the treatment. But a large city could be easily served by perhaps one large clinic with maybe four to six hundred medical professionals on staff (24/7/365).
Overall medical system costs will be driven down, but those remaining in the field would still be well paid --- they still have to be highly trained. Overall medical system infrastructure would be gutted. Ancillary services and industries would fail. All the people who work in those industries would be out of work. All the service industry people who rely on those folks' paychecks will also be hurting.
Eventually all these people would have to find something else to do. Eventually you might end up with a very attractive culture where people don't have to worry about disease & illness --- now you just have to solve the food problem! --- but in the meantime, it's going to be a very bumpy ride indeed!
EDIT: Since the nature of the question has changed, the answer will have to change too! Since the device does all the work, there is now no need for clinics or doctors or techs or nurses of any kind. For those who have the device implanted!
You say most people can't afford even the payment plan. Well, that kind of defeats your whole line of questioning, doesn't it? If 1% of the population (the uberwealthy) can afford it and no one else can, then what you end up with is a large number of wealthy social leaches who live disease free lives. Pretty much what they're doing now, living as they do in upper class strata of society which are generally much cleaner and much more disease free than the lower strata.
In reality, nothing much changes in the broader culture. The devices have only a negligible effect on society, because for the 99%, the health care system will still be needed and will still function as before the introduction of the panaceas.
Once it's in, why would you want it removed? It doesn't make sense to keep the fact hidden from the public. Reason being, they are going to find out the instant something happens. Because the first person to tamper with or remove the device isn't going to be some random homeless man in Ft. Lauderdale that nobody cares about (!). Us Magazine, People, E!, maybe even Ebony (or Ivory? if such a rag is even allowable!) they're all going to be filled with stories with headlines like "World Famous Singer R---a DEAD After Removing Miracle Cure Implant!! --- Shocking True Story Behind the Panacea of the Century!!"
As for why they aren't figuring it out themselves sooner: they don't know how the device works. If the company withholds design facts from their victims -- I mean, customers -- then no one will know going in. I'd put a penny to a pound that even if you made them sign an informed consent, people would still go for this device.
Actually, informed consent laws are what will do in your last paragraph. In the US at least, before any medical device can be implanted within a person, that person has to be fully informed of all intended and unintended results of implantation, including likely death by horrible disease if the device is ever removed.
You can't really pass a law prohibiting the tampering with an implanted device. Unless you're really prepared to police every implanted person 24/7.
So yeah, short answer is marginal effect on the broader society. I do think you need to clarify your setting and focus your question(s) a little more.