If you go to PPL sales in Houston, you can look at what some National Tradewinds have sold for in the past year. I would think that unit in good shape like mine would go for between $25,000 and $29,000.
If you can get info on upkeep that would help. Also check the build date on the tires and the batteries. You could be out as much as $700 for the batteries and $2400 on the tires.
If you have knowledge about MHs, you can check it out but you might want someone to give it a "once over" for you.
dons2346 mentioned they had one that wandered but I have not had any problems like that.
The Cat engine and the Allison transmission are almost bullet proof. Plenty of power for the mountains and you can expect between 8.5 and 10.5 MPG 68,000 miles is not bad for that year MH.
My wife loves our floor plan and we go every chance we can. Even though the National is no longer made, all the items that may need attention are name brand and are still available.
Best to you, Arnold
1999 National Tradewinds 7370
2014 Honda CR-V--Toad
Fulltime