Welcome to the QuiltingBoard, and what a great looking machine!
Are you sure you need the service manual, as opposed to the user manual? The user manual typically will have basic service information, unless you think something is out of adjustment.
If it were on my workbench, I would remove easily removable body parts and oil anywhere metal rubs against metal when the machine cycles, both in straight stitch and zig zag. If there are gears on top or bottom I would consider lightly greasing them instead of oiling them, but I think there's lots of debate on that.