Hi Atlanta,
Just saw your intro post (belated welcomes!!) OK regarding timing. Most LA timing setting is pretty universal. I have an Innova and they put up a GREAT you tube video on how to set the timing. It should translate to your machine. You are correct in assuming the machine skipping stitches may be due to your timing being off. It could be as simple as resetting your needle bar height. Try viewing ABM's you tube and see if any of the parts look the same and maybe this will help you.
https://www.youtube.com/watch?v=_D-6h9T7sn4
Now that box you pictured on your intro post is made by Pfaf. I would scrounge around on their site for contact info and see if they can't supply you with some sort of instruction manual for it. I suspect that box has something to do with setting your stitch regulator.
http://www.pfaff.com/
This also leads me to believe that Pfaf might also be the manufacturer of the machine and this Neal Iund you found may just have been a distributor of some sort. I think Pfaf is now manufacturing LA under their own name called Power Quilters. You may be able to find a saavy dealer for them that is willing to help you out with your used Legacy machine.
Good luck and once more Welcome to the board.