I think one of, if not the best class C out there if you go that way is called a Lazy Daze. Family owned company, that's all they make, in 3 sizes and several floorplans. There is cult following with these things. I have a used 92. There is a yahoo group:
http://autos.groups.yahoo.com/group/lifewithalazydazerv/
Company website is:
http://www.lazydaze.com/
I'm not sure they've made a diesel in more recent models, I think they have been using the E-450 chassis with the Triton V-10 for several years.
Born Free is another company up in Canada I think that is known to make a good class C RV.
I think you'll find for resale purpose a smaller class c will be easier to sell after your trip than a class a.
Good luck!