Thank you, geniescience and others who responded.
"The first response, from hj, said a lot in a few words. It could be argued that everything he didn't say didn't need to be said."
Others did add very useful information, to which I did reply, "Good info." I didn't want to say thank you till the end so as not to imply I didn't want anymore information. I didn't know anything about hazard pay, although I still don't know how much it could amount to. I understand that folks don't want to quote money, but asking for an approximate range, I didn't think was out of line. Regardless of the regional hourly rate, I also thought it was fair to have someone more clearly define hazard pay. 1.5x normal rate, doesn't disclose anything too specific, but gives me a very good idea as to what to expect. But if no one wants to tell me any approximations, that's fine.
I have spoken to friends, neighbors and family. Most of whom do for themselves and have never called a plumber. I would rather do this for myself, which is why I also asked about how to safely do it. No one has made any suggestions though. If I knew a snake would retrieve it and not push it down further, making it even more costly to retrieve, I would surely try that.
About diagnosis, my friend who helped me first, didn't think that the vent was obstructed. We tried several things, none of which worked. I did have a diagnosis discussion in this forum earlier. No consensus was reached - which is hard to do not having it in front of you. My dad was over recently and he is pretty convinced that it is in fact obstructed. I agree with the points that he made, and am reasonably sure that the problem is in fact due to a vent pipe obstruction.
In my diagnosis discussion, I stated that the problem happened all of a sudden, in the middle of winter. So, I don't think it is a leaf buildup, but rather a bird/nest or squirrel. Here & now, I did not restate all of the diagnosis info, but did theorize that it was an animal. It seemed reasonable to me that for someone who does this type of job fairly routinely might be able to tell me if it 'usually' takes less than one hour or multiple hours to remove an animal. But then again, I still don't know the normally used method(s) used to remove obstructions. Is it one method for leaves and another method for dead squirrel? A combination method for bird/nest?
I am not the expert, so I don't know all the right questions to ask. Thanks to all who have helped and/or might respond further.
DavidD