Hi Mardonahue,
I've just recently got my MMJ exemption from my family doctor. It's good to be educated about it before going in, as with any medication. Make sure your doctor knows that you approach MMJ just as you do all your medications and that you will treat it accordingly. Many physicians will have you sign an agreement with them outlining the terms of use and this allows them the ability to terminate the contract if they feel that you are not using it as agreed upon (for example it may say you can only get an exemption from them and that you must attend all your appointments, and complete drug screening, ect). Your GP may be more willing to do a trial of MMJ if you fill out a contract with them.
In Canada, you have to register with a specific distributor, which can be agreed upon between you and your GP (I personally use Cannimed but you may find one you would rather use). Once you fill out all the paperwork with your GP and the distributor you will be able to purchase MMJ based on your prescription (although in Canada it is not a prescription just an exemption - many physicians take the wording seriously). If your GP is hesitant you can always ask if he would be willing to do a 1, 2, or 3 month trial only.
Just so you know, in Canada, physicians cannot deny a MMJ prescription (or any prescription) base on the fact that they don't agree with it. They must have a legit medical reason that they do not feel a specific medication is not right for you. They can get into big trouble with the college if they use a blank statement in their practice saying they don't prescribe MMJ, or narcotics, or stimulants, ect. In saying that, a physician can easily get around this by saying that they do not feel they have the expertise to prescribe and monitor a specific medication safely for your condition. I've heard of people complaining about their GPs to the college but it can easily backfire. It's best if you just have a face to face sit down and discuss your options.
Another suggestion - use a vaporizor or once you know your daily dose you can use edibles but most physicians will recommend a vaporizor anyways.
Best of luck with you. Let me know how it goes!