Infra-Red In Ernest
For a still subject, not too much difference but for a moving one...the difference between getting the shot sharp or as a complete fuzzy blur. You can use the normal aperture controls on your lens.
Of course you are sort of making a long-term IR commitment with the camera conversion and you will get a monochrome image. You can get wild colours if you put them into the file afterwards.
Call the repair department and discuss the technical details and costs with the boys.