1990 Intercooled 12v/H1C WH1C Turbo/ nv4500/4.54FFD60/1995 ford E350

I didn't think.. Or rather hope, my fummins van would need attention so soon.
It ran great unloaded back home(29 mpg) but when I hauled my 8000# toyhauler ,which is what I bought it for, and ran it hard up the Rockies, it ran like crap. Post egt's flew up to almost 900 running only 65 mph mid day on the plains. Seemed like 4.54 was just a bit to tall and I was always shifting between 4th and 5th unless I had a tail wind.. It now has white start-up smoke until warm and leaks oil bad even though it never over heated. Turbo post egt's ran between 700 and 900 the entire trip. Just got back, and haven't pulled the dog house yet.

Anyway.. Can a person with only gasser rebuild experience rebuild a 12v from geno's factory service manual CD?

And where can I learn about rebuild mods or combos for towing performance? Budget is fairly open.. <$5k?
thanks