Guider 2 lid and self leveling question

I bought a used Guider 2 (my first 3D printer!) from a guy who said that he had bought it used himself. He decided he didn't want to spend the time getting it up and running, so he let me have it for $100. Anyhow, to get to the point, I've gotten it up and running except for the auto-level function. I replaced the sensor, but that did not fix it. I can manually level the bed, but it would be nice to get the auto-level working. Any advice on what I might try next?

My other question is what to do about the missing lid that I'll want for printing with ABS. I haven't been able to find one online and haven't found anyone who has designed one that can be printed. Could I just make a tent out of plastic film? Should I teach myself how to design one myself?

Thanks!