My plane is currently down getting an engine overhaul. Before this, I was having an issue with my Century HSI and/or Bendix GPS. Some Googling leads me to believe it is probably the HSI. There is an avionics shop on the field; can I pull the HSI and bring it to them to test and see if it needs to be overhauled/replaced? I’d like to deal with this now while the plane is grounded anyway. Would this be in the realm of something the average avionics shop could do?