Passenger side wiper failure

[E53fan16]

Hello Gents,

My passenger wiper crapped out on me Tuesday, it moves only two inches on each wipe maneuver. Took it to my independent shop and the mechanic said I need a new wiper motor upon picking up the vehicle. How do you diagnose needing a new wiper motor vs just having to tightening the bolt that I have reading people mentioning in the threads here? I don't want to spend money unnecessary if I don't need to. Obviously, this would beneficial for the independent shop as he quoted me at $675 wiper motor, $150 wiper arm and $150 for labor. I asked him why he took off the wiper arm, he said it's not working and I need a new one. Something is not adding up....

Your insight is appreciated!