Hi, I've had my JD 755 for 25 years and have found it to be be an excellent machine. I've only had 2 problems in the 25 years.
First was a hard hydraulic line leak and second a fuel delivery problem. I was able to get clues on the fuel problem here on the forums. They lead me to finding a corrosion problem on a fuse. It was very helpful for the fix.
The 755 has been a great machine and TractorByNet a great source of information.