In your place, I would still go ahead with what they told you (the X-ray and final consultation), so as to have the complete record that you have been found all clear at this time, JUST IN CASE the issue crops up again in the future.
what is the difference between work visa and work permit?
Since 2010, NZ doesn't use the term 'work permit' any more. A visa is what gives you the right to live and work in NZ, for whatever length of time and under what conditions it states.
How soon can I apply for PR?
If you get a skilled job in NZ, for which you have the necessary qualifications, meeting the conditions mentioned for applying for Residence under the Skilled Migrant Category, then you can put in your EOI immediately. See the various INZ web pages on the subject. Start here
http://www.immigration.govt.nz/migra...nt/default.htm and follow the links through the whole section. (However, the points indicator can be misleading, so I recommend looking here
http://www.immigration.govt.nz/opsmanual/6954.htm instead. SM6 has a chart with all the points, and the other sections have the regulations needed for claiming under each heading.)
Notice, it is Residence you would get first if successful. PR is a different visa that you could only apply for after living in NZ on a resident visa for a minimum of two years.
My wife is a student in NZ. Any chances of me sponsoring her in the future or will I need to be a dependent?
If you get residence, or a work visa in your own right, you could include your wife in the residence application, or sponsor her for a partner-sponsored temporary work visa. Or if she gets residence or the work visa first, she could include or sponsor you.
If I join an accredited employer, are my chances of PR brighter? I understand that the minimum wages must be at least NZ $ 55000 per year.
If you are offered a job by an accredited employer, they are able to sponsor you for a Work To Residence visa, which will enable you to move on to a Residence visa after two years working for them. So the fact of going to an accredited employer has the advantage that you know from the outset that you WILL be able to get Residence if you stay with them. Here are the details about WTR.
http://www.immigration.govt.nz/migra.../caniworkinnz/ And here are the details about applying for Residence From Work after the two years.
http://www.immigration.govt.nz/migra...iworkfromresi/ (That is when the requirement comes in for earning a minimum of $55,000 a year.) Also, if at the end of the two years, you are earning a minimum of $90,000, you can be granted PR straight away, not having to spend the two years on Residence first.
http://www.immigration.govt.nz/opsmanual/30628.htm
But some people on a WTR prefer to apply for Residence under SMC straight away. The Residence gained is just the same by the two routes. The advantage of having Residence over having either a temporary work visa or WTR is that those are both limited to working for one, named, employer, whereas with Residence, you can go to any job you are offered, skilled or not.