Our '82 380SL hasn't been driven for about 8 months.
During a normal start up, shifted into reverse and from that point on it will not come out of reverse, yet the shifter will go into any position with almost no resistance

I checked the linkage, and it seems to be intact.
The fluid level is right and it smells and looks good.

I bought the Mo 107 service manual CD but it doesn't really
incorporate transmission issues.

Can someone point me in the right direction?
(even if it's to the dealership).
I'm curious to know what to expect.

Thanks, Buck

Trans problem
 

I would recommend you take your car to a Mercedes Specialist who repairs transmissions also. I work on these transmissions and it isnt something anybody should just dive into. If you decide to get into it yourself it could be more expensive than the original problem . Just a recommendation.

Did you look at the linkage under the car? It sure sounds like your linkage came apart. It could happen inside the trans but is more likely right at the base of the shifter (If it happened at the other end the link would bang around).