I have a chance to buy a CR5M. Are some years models better than other? Did they change something over the years? And what do you consider a good price for a used one in good condition? including the Tripod and Frame strap system (not sure if I need that but it is included). I can not test it beforehand so I have to buy it unseen. I am a little anxious for that. Is there something else that I have to take in account that I might not think of?