There is a Yahoo group dedicated to older Berninas, called "
Bernina ThirtySomethings". I lean towards repair pedals when possible, a new Bernina pedal tends to cost a bit. It can be a minor thing, hard to know. Some models take well to generic pedals though. It takes a general
Bernina Bobbin case; same as some current models. There are generic cases available, but there are lots of confused info on model compatability.
It's a very simple machine to use, easy clean and maintain, and yes much the same as the 830 Record, but with less stitch patterns. The 831 has turn dials (all the 800s does), and it has the same set up as the 830 Record, the same buttonholer. It's very forgiving when it comes to various fabric thicknesses, not as easy to give a full service, at least not as an amateur; but with help and good info anything is possible.
There are various bobbin cases for different type of work; cordonette and one with a black hatch. It needs to be confirmed, but I think all listed for the CB hook type should work with your machine.