2003 Ford Explorer Some advice please

Hi We have just purchased a Ford Explorer in Auckland. It was an import from Japan. Great car but seem to be having a few problems that could be related to each other. When my husband brought it home the other night there was smoke coming from the passenger rear, when we looked the disc was glowing orange! We contacted the company and they came the next day to collect it. They say that they had a brake specialist look at it and has said there was nothing wrong with it and that we could have been driving with tha handbrake on or my husband had his foot on the brake all the way home! Yeah right! So we have had the car back to discover a grinding sound at the rear end when turning. We stopped at a ford garage and the guy there sat in the back a felt the grind and said you need to take the car straight back to where you brought it from as that is a diff problem. They have had the car back again to fix but as we are waiting to hear we just wanted to know what you guys think. Sorry to sound so vauge but not to good with cars, thanks