I am taking a non bearing wall down that has electrical work in it, including a 3 way switch for a single light. I want to disconnect this switch so the other one works. How do I do this?
You will have to trace the wires. You can look at How exactly does a 3-way switch work?. You should replace the remaining 3 way with a regular single switch and wire it normally to the light fixture.
It depends. You might be lucky or not, depends on which way the wires go. Note that any any splices in wires must be accessible for future work.
Start with https://diy.stackexchange.com/a/4054/5960 and post some photos.