Hi Jessica...
First, congratulations on your upcoming wedding!!
Disney Fairy Tale Weddings are very "protective" of their services. Unfortunately, that means that they only allow/permit on property weddings to go through them.
Your best bet for a simple ceremony would be to do the "intimate" (now called "Escape") wedding. It basically includes a small ceremony (at one of five locations), flowers, cake and champagne reception, violinist, photography, limo service, and you would contract with an officiant on your own.
Try this link for info
DISNEY WEDDINGS
That's really the best way to get married on property at Disney. I have heard of others who have considered "sneaking" a ceremony in their room. If you choose to try to do that, you might find that some officiants (who have good relationships with Disney Weddings) will not be willing to break Disney's rule. It is also possible that Disney could go so far as to ask you to leave the property. I guess it depends on how much risk you are willing to take.
Now, there are other locations (outside of Disney) where you might have other options.
You can try
Orlando Weddings and you can also try something at the Swan and Dolphin. You can also do a google search for "Orlando Weddings" and read through some of your options there.
I hope that helps!