Hi different expert here.
I have worked on these for many years and with this kind of problem you really need an expert to look at this one. The problem could be one of many and it would cost more to just blindly begin replacing parts you don't need;-)
They will get you going faster and with less grief and cash outlay.
I wish I have better news but thats what I would do myself if faced with something like this.
At least the original owner seems to have been honest with you.
Lol, we will see.
If you need help locating someone near you you can always contact Sears, they have such a service local to anyone in the US;-)
And they are fair and honest.
Please rate my service to you kindly before you go, and that way I can stick with you until this if solved. I will help you anyway I can.
After you rate, you can then contact me any time by simply replying to this message.
Have a great day and best of luck with this unit;-)
I can tell you it is a good quality machine.