Modding a DSLR camera for astrophotography involves removing the standard filter (which blocks too much of the red spectrum which is an important part of emission nebula) in front of the imaging sensor and replaces it with an astro friendly filter to allow those red spectrum wavelengths through. It is a step not to be taken lightly as it will invalidate your warranty and make daytime shots not so great unless you purchase a removable filter to allow for both purposes. Cost varies due to filter and labour costs but will likely add a few hundred to the cost. I don't know anyone in Perth who does it, I had mine done while visiting Hong Kong. Resale of a modded camera on IIS would be good, not so good most other places. Hope that helps.
