OK, I know how to get to the stern of the Wreck of the FMS Northern Star, but how do I go to the bow from there

That is, get through the barrier on the aft deck?

The top aft? There's a large gate you can open to progress to the bow.

boy was that place creepy the first time i found it )

Barrier? To get on to the aft deck requires going into the hull space, jumping up on some containers, and following them back. This will lead you right beside the conning tower at the rear. Then, just walk straight through the containers to the bow (and be sure to collect the reward there - it bobbles ).

Don't forget to read the magazine while you are perusing the ship.

Meh. There are better magazines out there and they're actually useful.