Help Fix My Car?!?!?

So every time I feel like maybe I have a little solid footing... My car recently died on me, a transmission issue. Since pretty much no one I know is familiar with transmission, it looks like I need to go to a professional. They're quoting me $500, for starters. I can't keep up with this, but without a car simple two errand runs become all-day affairs. The bus stop is still far enough away from my house and comes by so infrequently that groceries trips can no longer include refrigerated food. I need the car... Please... Help?