O OK hun, I can help you there.
Undo all the seaming for the sleeve and the side seams. Leave the shoulder seams intact.
Now fold your sleeve in half and mark the center.
With right sides together, center your mark over the shoulder seam and make sure that you have equal amounts of sleeve on each side. Double points work really well for using as "pins" to pin it into place. Just remember to pull them as you get to them, just like in sewing you pull the pins when you get to them so you aren't sewing over them. Seam the bound edge of the sleeve to the body of the sweater. Do the same for the other side.
Now turn your sweater insideout and match sleeve seams and side seams. Pin carefully with dpn's making sure to pull them as you get to them. Now sew the sleeve and side seams in one fell swoop. Do the same for the other side, making sure that you start at the same place. Either the bottom of the sweater or the cuff of the sleeve. That makes sure that the "grain" or pull of your seams don't pull in opposite directions.
Hope that helps hun.