Partial dislocations 20 years ago without repeat to me does not necessitate immediate MD visit. As a patient, I try to gather more info on if, what, when, how 1st if I can. Many,many times the patient will tell you what you need to know because they have observed the behavior of their problem. You are an active part of your diagnosis and healing. Surgeons are necessary when they are necessary but they also only operate on about 25-30 % of their caseload.
I don't know how the health system works in Canada. A visit to an ortho here would involve some physical tests and an x-ray which will only show joint spaces and bone spurs. If that is you problem then they would give you the option of a steroid injection and send you to therapy. In light of no results they would then send you for an MRI.
A good seasoned orthopaedic therapist will be able to discriminate and rule in or out shoulder pain based on various pathologies. There are valid and very sensitive and specific tests that are available ( see Chad Cook - ortho physical exam tests an evidence based approach). A good experienced orthopaedic therapist is not only trained to do exactly that but also prescribe a plan of care. If you can directly access a good shoulder therapist I would go that route 1st. You will be there anyway. There is nothing wrong with finding out what affects your problem if you choose to do so. As an orthopaedic specialist I ask my patients to do so in the clinic and for homework. Cause and effect is very powerful