To be honest I would loook at the options of a fully built engine also. Loads of the gang do em on here and for very good money. Im looking into a few options my self.
I expect u are like me keen to do it for your self but there is a very very bad side to it however. I have rebuilt the head on mine 3 times to the book and every time it has had a problem once rebuilt.
The other good point here is you have any problems they will be willing to help you out and should offer a warrentyl

As for your shells mate,

They are basically a bearing which goes between:
Mains - Block to Crank
Big Ends - Crank to Conrod big ends.

Speak to some of the traders on here.