Vray is just one renderer, and although it can produce very nice results its not particularly easy to get the hang of. If your just starting out with rendering id recommend having a look at twilight: http://www.twilightrender.com/ and podoum: http://www.suplugins.com/
And no, your model doesnt necessarily have to be very neat, although you will need to do certain things to make it look reasonable, for example making sure all the faces are pointing the right way and making sure the right bits of line work are smoothed.