To DP or not DP

Couple comments, 138k miles is certainly NOT "long in the tooth" for an engine that OTR truckers regularly get a million miles on. That's just over 7000 miles/year, about average. Another thing would be to look at older units to see how they have held up. Most RV's are built to a price point, IOW as cheaply as they can sell them. Newells, as a few others, are built differently. Newells are all custom built to the owners specs. Most of them weren't looking for a bargain apparently. I've previously owned a '93 and '98 Newell and found them to be very solidly built coaches, certainly in the very top of quality. I currently own a 36' 1999 Foretravel mainly because Newell builds mostly 45' coaches and we wanted smaller for our Alaska trip. Newell is still privately owned and has great factory support. A great forum to get info and answers is www.newellgurus.com
And remember like all others maintenance and records are very important.
Good luck in your search.