I have a set of cams for a Kenmore 158.903 (which I love). that I would be willing to part with if you are interested. My machine looks just like yours but I can't be sure if these cams will work on yours. Maybe someone on the board knows. I also have the original manual (50 pages) for the 198.903 (not for sale as I really use it quite often) so I can possibly help you out with any problems you may have with threading, bobbin winding, stitching, etc.
If you really need a manual and can't locate one, let me know and I will try to scan mine and send you a copy of it. I also have a Sears buttonhole set that came with my machine (that I never use).