Is the bobbin in vertically or does it drop in horizonally. If it's vertical, there is a little flip release across the middle. Flip it out and it becomes a little handle for removing the bobbin. A drop in should just lift out. The vertical is great for FWQ.
Take the machine apart as far as you can - top off - bobbin race out and clean everything with sewing machine oil. You'll be amazed at how well the old metal machines sew, but you'll do it no favors sewing with it dirty.