Worried about 1986 mercedes 300e passing CA smog.?

I worked on a few.. Go down to the auto parts store... Have the pull up the codes... It's free... It will tell you witch one it it. Fix that and whatever elas it needs... As for the starting in neutral only... Most likely your neutral switch is bad or some you can adjust... After you have had the repair done... Go back to the auto parts store and they can erase the codes and you will pass... On some Mercedes it is not recommended to clear the codes by battery disconnection... Good luck. They will have to order the parts...