The 3004 will work on the elevator and ailerons, however I'd buy something more powerful for the rudder. Maybe a Hitec 605 at least. You could get one of those for under $30. I'm using 3001's on the elevators and ailerons and they are working fine. The plane will fly better with high-end servo's, but that would also increase your cost tremendously.

If you already have the YS, then you should do it. It's a great engine for this plane.