@mobpapst: a screen with what you got would help give you directions. Regarding using the symmetry modifier, before applying it go un the Hierarchy pannel and click "Affect pivot",then on the front view bring your pivot to the place you want it to be the center of the symmetry modifier. Then apply it :) As a side note,you…
I modeled your object a little bit, the proportions are incorrect but I hope you find it useful. The basemesh was made from a box primitive. The polycount is kept as low as possible for easier editing. Most of the control loops are generated from a modifier equivalent to the bevel modifier in blender