Briefly..
If your licence is Canadian and you are valid and current in all your ratings, there are three broad categories to get the JAA licence (assuming that is what you are talking about)
1) Below 1500hrs TT - 650hours min ground school theory. Can be done distance learning with certified FTO or integrated full time. Cost can vary greatly. 14 written exams. A world apart from the Canadian CPL written / SAMRA and SARON. Be prepared for some hard study! Then min 15 hours conversion training for the IR (5 plane 10 sim but normally more than mins are needed) Cost - about £12,000 absolute min including ground school and fees.
CPL test needed too, but training as required (normally 5-10hrs in a complex single i.e. PA28-200)
2) Over 1500TT - study as required and recommended by an approved FTO. This does not mean you can just sit the exams. If you did, believe me you would not pass them! A lot of FTO's recommend you sit their full course as the cost difference can be negligible.
3) If you have a certain amount of time (think its +3000TT) and over 500hrs (command?) on a JAR/FAR 25 aircraft, then you can do your conversion training on type and need to sit just two written exams, without going through a groundschool FTO.