The sensor has red, green, and blue micro-filters over individual pixels (see
http://en.wikipedia.org/wiki/Color_filter_array ). As such, you wouldn't gain anything with broad-band colour filters that you couldn't just get with processing in your favourite photo app. Narrow-band imaging of the ionisation lines of Hydrogen and Sulphur are where the real value lies, as these fall at the upper end of red and beyond the range most built-in IR filters will block. The camera is still best for wavelenghts that fall within visible light, as the RGB filter is still cutting off most wavelengths outside of their designed sensitivity range, they just will not cut them off quite as sharply.
You still need a monochrome array without the bayer matrix in order to effectively image in wavelengths deeper into IR and UV.
The mods themselves are not that hard if you are handy with tools and have steady fingers, but go into it knowing that there is the real chance of damaging the camera beyond inexpensive repair. It took me a week to get the mod to my old 10D right, since the silicone I was using to hold the replacement glass in place kept getting where it was not supposed to be, and cleaning that up was a challenge. My wife also hates me for "wrecking the old camera" (her words) rather than selling it. She could care less if I can shoot in IR now
