To simplify things, you might want to split the model down the middle and delete the half you won't be working on. Once you get the arm all stitched, you can mirror it for the other side.

Make sure that when you detach and such, that you press the "3" key to put everything back in hi-res mode, as some pieces usually revert to '1' - low res setting.

You'll more than likely want to add a few isoparms in that neck area.

This takes a bit of practice... you'll probably need to go through the process a couple of times to get the hang of it.

Also, you might find the VIP video version of this tutorial here at SM helpful. The scene file of my muscle man is included.

Also, I would recomend that you totally "finish" the form of the arm and torso before stitching, as continuing the model afterwards can be a little difficult.

Good luck!