[tsubaki]

On 1) the plastic bushings in the outside center are usually the culpret. They look like a thin piece of pvc pipe. Either one where the shifter handle connects can cause that problem. These boxes are reversable for right or left hand operation.
Don't get too anxious, parts cost more than the unit.
If that ain't plane enough let me know.
Usually all they need is greasing (fill it up)
On 2) make sure the cables are adaptable for your year motor.
I agree with Blue, but if you do go universal there are a lot of choices.