You are on the right track.
One suggestion, try modelling without the subsurf so you can clearly see your topology.
You have very good blueprints, so just try to match your verts with the sketch. Connect the dots sort of
I guess the thing is to keep going. Save a copy of this file so if you goof up you can revert to this one. Yeah just keep modelling, you can’t break it! And if it seems like you just don’t know what to do and that you just can’t model, remember that all of us Blender users were once at that point (and many still are) and just the more modelling you do, the better you get.
Hope this helps.