You certainly can convert the camera yourself but it's a complicated procedure that involves dismantling a lot of the camera. Unless you've done anything similar before I wouldn't advise it.
There are two companies I know of in the UK, Advanced Camera Services (whose website seems to have been hacked) and ProTech. I had a 450D converted by ProTech and was very satisfied with the service. Conversion of an APS-C body costs £250.
What you've heard is sort of true. Canon lens coatings transmit less infrared than Nikons, which make Nikon lenses slightly better for IR work overall, however any lens used for infrared is operating well outside of it's design parameters and performance is unpredictable.
Ultimately you need to try a few lenses and see what results you get. The good news is that there are some very cheap lenses that perform better in infrared than their much more expensive top of the range counterparts.