I rebuilt a used car from the chassis up, including rewiring and brake pipes. I was in the same position as you, but I got loads of help from blatchat, and one of the local members even came round with an engine crane and helped me put it and the box in.
Don't underestimate the power of this forum for assistance. It's like having hundreds of knowledgable mates.
So in summary, it stretched my abilities, but I learned an awful lot, I have a car that I know inside out, and it gave me a great deal of satisfaction to have done it.