Stop writing now! If you intend to get published by a publishing house, you have to be careful with completing to much of the manuscript up front. Sometimes the houses like to have significant input in terms of the content or where the plot goes. With a complete manuscript you may want to solicit an agent.
However, if you know you have a solid concept and do not mind potentially waiting for a response (which may take longer), then keep writing and complete the manuscript. This is especially true if you plan on self-publishing.