I believe the front engine cover is made using some of the roof from the shorter box car , it seems reasonably straight forward .The cab though seems to be a lot of cutting and glueing to make it. The powered version instructions seem to be a little vague as well :-(
I like some of the alternatives on one of the instruction sheets , they are shorter and generally look a lot better than the standard version .
This will be my next HO kit after finishing my Bunkhouse i am building at the moment , and i have been volunteered to make a class A climax dummy in Nn3
Cheers
Ian