It can be pricey to have your existing motor serviced, painted, plated, restored, and fully functioning and looking like new. For some repainting their cars, and going through the restoration process, it is worth it.
The motor will blow fuses when it's pulling too much current. It does this when it gets old, and the internal bearing surfaces are drying up. Also, the arm mechanism it drives can be getting harder to move. To repair, one pulls the motor and services it, or replaces it with another used one. In the process, the mechanical parts inside the cowl are inspected, greased, tested, etc, to make sure their in top working order.
You can drop a new reproduction motor in, but that may be just as pricey as having your old one restored. Plus, if the friction and current draw is caused by the arms functioning poorly, or even jammed up, you may cook the new motor.
You've got some work ahead of you. But, there is a long shot it's simply a short. That would actually be a good thing, if it was a short, because fixing the short will be considerably less work, maybe even less expense to repair.
So, as EW1BH27 says, test this by disconnecting the wiper motor, and activating the switch to see if the fuse blows. You said the shop did this? Okay, then seek a second opinion. Do the test, yourself. You've got much to gain if it's a short, and lots of time and money to lose, if it's not a short, and the motor or mechanism is the problem.
