Suki, congratulations and jubilations
You chose a marvelous place to get married, but I am biased, Negril is home, LOL.
It can be done on your own. I would not say, yes or no, it is up to the individual to decide to use a consultant. However, if you wish to do it on your own, then I say more power to you. My recommendation is for you to take the following steps first:
1) Download all the forms for sponsor and applicant, including the region specific guide for the applicant and the document checklists. See here:
http://www.cic.gc.ca/english/information/applications/fc.asp
2. READ ALL THE FORMS. One by one, separately and together with your partner, so you both understand what will be needed from you both.
3. Check out the following link to the manual used by immigration officers to process overseas applications:
http://www.cic.gc.ca/english/resources/manuals/op/op02-eng.pdf
That's right, the process is laid out there for you to see what the immigration officer will be measuring your application and relationship against, so READ IT.
Take your time reading the manual and the forms. When you have done the reading (more than once!) come back for more advice and info. Happy reading!