Give it some thought. These bikes are like a simple farm tractor; easily maintained. There are some good web-based, self-help BMW articles available to assist in building your confidence. Plus...
Monte is absolutely right. One of the chief joys of an airhead is being able to fix it yourself. I've serviced my entire rear drive, including seals, bearings, and brakes. I might draw the line at replacing the gear set, but the rest of it is within the reach of any reasonably competent handyperson.
I don't think it was sabatoge. It seems unlikely that anyone would carry around just the right size wrench to undo an axle bolt. Two wrenches, actually, if you count the pinch bolt. Perhaps a little periodic maintenance would have caught the loose bolts before they became hazardous.
Steve