We just about bought a Grand Design and first did some research on quality and found that it is not just GD with issues but most of the 5vrs. Unless one buys the oldie but goodie around 2009 and earli...
I keep up on regular maintenance and service on both of our motorhomes and I can say that we have had 1000's of miles of trouble free vacations. The diesel maintenance costs more than the gasser but we've never had a ruined vacation due to a breakdown from either one.
It's entirely possible to find a good DP in the early 2000's but you may have to up your budget closer to 60k for those years.