Dear Shauna:
How do I find a publisher? Do I need an agent?

Test your manuscript on friends and other writers before taking it to market -- you don't get a second chance. At the same time, don't over wordprocess/self-edit/self-copyedit or you'll end up with a m/s where the image of the word on the page supersedes content.

I believe writing a novel is primarily an act of communication, so communicate it while you're still this version of yourself and ready to wrestle with the theme(s). A m/s that sits with its writer for more than four-five years is likely to be over-worked, because it's common for the writer to change by the process of writing (at least in the literary fiction genre). I'm not sure what is 'completion' anyway -- I forget who said a novel is never finished, but at some point is abandoned.

Make sure you select readers who will be patient with raw text. It's also not a bad idea to shop a first novel m/s to a couple of publishers yourself (and I stress one or two publishers only) and when you get any interest/feedback, call an agent. The agent can take it wider, do the sales negotiations so that you keep your relationship with your editor free of the question of money. AND I suggest, particularly if you live in N. America, call a book attorney to review any contract your agent sends you. The Writer's Union of Canada can recommend a book attorney.

First novels are not very difficult to sell. What is difficult if you are from a minority culture is to find an editor in North America who understands what you're trying to do and who will not be too respectful of the text nor too interested in "the market"  (a code phrase for "the non-minority reader"). Someone who wants it to be the best damn story and prose you can possibly ask of yourself. So, unless you're writing something topical that has a shelf life of a year or two, (not likely with fiction and even less likely with literary fiction) find an editor you can trust with your writing career, not just a publisher. Someone older than yourself will be more able to hone your writing, too.

Best of Luck!
Shauna