Yipes! Spendy machine...I'd either find myself a "real" 'lectrician or better yet, a sewing shop that you can hold liable if they screw it up completely.
OTOH, if you're going to have to buy a whole new one anyhow...what do you lose by having someone (who pretty much knows what they're doing so they don't blow up the machine) see if they can fix it... Just a thought.
In any case, what an absolutely *frustrating* problem. Glad your mom has one you can use...hope you find some resolution that costs less than $400...that could *really* cut into a girl's fabric budget!
Good luck!