Well, eek!
The IT support market has to contend with an awful lot of erm...amateurs. In the last five years, every builder, plumber and his dog reckons they can make serious amounts of dough from support jobs. The shear weight of CVs that are binned by personnel depts is outstanding. As a supposed IT pro, naturally I should discourage your career move in small part to further mine!
Seriously though. Having exposure to Linux is good as Windows-only is limiting somewhat (I should know). You'd probably end up with a 1st/2nd line support job for about 15-18k. After 3 years, you could get up to around 25k if your lucky and has gained enough skill through exposure to the job.
Industry qualifications (microsoft, cisco) etc are ten a penny. If you know your stuff/are a birhgt spark, then get one. Unfortunately for some, a portion of people who have successfully gained these quals, still won't be able to diagnose an IT problem.
With some employers, these quals are a necessity for application. But with others, for the aforementioned reason, these quals are something to be wary of! That is, having one does not mean you are any good.
I touched upon diagnosis. If you have the ability to communicate with a normal user in simple English terms, diagnose and fix the problem in a jiffy, then you've got it made. Nevermind what you know, it's more important with how you go about doing it.
Be sure to apply this in the "transferable skills" mention for any interview. Being in a cockpit, you would often come up against tech probkems which would have to be solved in a similar manner as above.
Good luck! I also hear that NZ are crying out for proper IT pros.
=Neil=