It is not the same as the green card, but a different visa that will only permit you to work there.
One needs to go thru the same procedure for any country that they wish to be able to work in. All require licenbsure as well as immigration to get a visa to be able to work in that locale.
The visa that you will get to work in Saipan is only valid for there and cannot be used to even enter the mainland of the US. Much has already been written on this topic and there is no reason to use an agency either. They cannot do anything for you that you cannot do on your own, other than take your money for providing a service that does not need their help to begin with.
Not sure what you are speaking of; if it is hospitals, then you are going to need to do your own research and contact them directly. Be aware that it is also quite difficult to get a job there at this time as well, since they have many more applicants than they normally need.
Just take the time and you can come up with the list of the facilities that are there, and even if they are hiring at this time.