apower,
You should start by ordering a copy of his service record while he can still sign the letter requesting it for himself. If he orders it, there won't be any deletion of information based on privacy issues.
Instructions can be found here: http://www.collectionscanada.gc.ca/genealogie/022-909.007-e.html
Also, try these old threads:
3rd Anti Tank 1944 - http://army.ca/forums/threads/16951.0
3rd Anti Tank Regiment - http://army.ca/forums/threads/50271.0