Pardon this posting...need some legal advice

I am not an attorney ... three questions for clarity: 

1) The "him" below that signed the Bill of Sale is the "co-worker"?  This in essence would give you two documents the co-worker signed: the original "Finance Contract" and then the ensuing "Bill of Sale".

2) While not said, it appears that the sole name on the title of the vehicle is your co-worker.  Who is carrying the insurance on the vehicle? 

3) Why are you fearful that he will not sign over the title?  He has already signed the 'Bill of Sale' ...

1) The "him" below that signed the Bill of Sale is the "co-worker"?  This in essence would give you two documents the co-worker signed: the original "Finance Contract" and then the ensuing "Bill of Sale". 

Yes -- "him" is the co-worker.  He did sign both the Finance agreement with me (which he is already in default on, since he did not make the first scheduled payment.  And, he also signed the Bill of Sale, agreeing to sell the vehicle.

2) While not said, it appears that the sole name on the title of the vehicle is your co-worker.  Who is carrying the insurance on the vehicle?  

You are correct again.  The only name on the car was his because I had loaned him my extra car a couple times but I was not crazy about the idea of him driving around in my car with my insurance.

3) Why are you fearful that he will not sign over the title?  He has already signed the 'Bill of Sale' ...

He actually had the audacity to tell me that he now wanted the car back -- likely because he's back to riding his bike and taking the bus to work -- after I had already sold it.  The other thing he asked for was more money, saying that he wanted to sell it for more than it sold for.  Problem was that he was being shady when I told him that I had some potential buyers, so I sold it to the first offer I received, rather than holding out for a few extra hundred dollars.  He has also now gone to management at work and tried to involve them, despite the fact that this has nothing to do with work and is a personal issue.  Trust me, he is not going to relinquish the Title without a fight.  Despite the fact that I have now already given him $4950 as an act of good faith and tried to help him in his quest for transportation.  It's truly mind boggling to me that he has taken this route, but he has, so now I am trying to figure out my options.

Don't, however, let this dissuade you from doing good deeds like this in the future.  One bad egg such as himself does not mean that the others are as well ... just continue to be careful.

big john speaketh the truth.  It's not uncommon for people to not have a copy of the title to a car, but the DMV has a record because of taxes and the tags.

FWIW, there is also a place on the title to write in that you have a security interest in the car.  Once you fill that in the car can not be transfered without your signature.  That's how I have protected myself in the past when I helped folks buy a car.