We have a 1999 Gulf Stream Sun Voyager, the biggest draw being that my wife fell in love with the floor plan. We were told about that "great Amish craftsmanship" which sounds better than it is. When ours was the same age as the one MH you are considering, everything was fine. Now that it is a few years older, ALL the fabrics are nearly threadbare and we are looking at either recovering or replacing all the furniture. Fuses are scattered all over the place, so when anything electrical fails, finding the proper fuse can be an adventure.
The chassis is Ford, so chassis reliability has been like like any Ford truck, very few problems and those were easily fixed. I realize you are looking at a diesel, but remember the chassis and the coach are separate entities with different issues.
Would I buy Gulf Stream again? Probably not.