Hi Andrew,
I know that this whole thing can be overwhelming. It's also true that there is a fair bit of physics and maths involved.
As for the hand-book, well; the real thing is a multi-million dollar machine that is meant for experienced operators. As such, it is normal for aircraft to have nice thick hand books.
Furthermore, all this jargon can be a bit overwhelming and intimidating.
To address your first point regarding the calculations, I would personally not do them. I'd check in the manual the speeds for a fully laden bird and always use these speeds.
This is will safely see you through. The only side effect of this is that when less loaded you find yourself airborne at speeds lower than the maximum weight ones.
There are indeed many excel spreadsheets to do these calculations quickly but they usually dedicated to a plane type. What works for a 747 will not be the same as your ATR for example. Hence it is rather difficult to find these unless the handbook itself has some links.
If you don't know what the speeds mean and other jargon then a good place to start is a link proposed by Hector Partidas:
http://www.luizmonteiro.com/WBC.htmI hope this helps you although, as I said earlier, I don't see that you need these calculations until you start strecthing the operational limits of the plane, the airodrome and prevailing conditions.
Till then, take it easy, have fun and don't be afraid to ask.
All the best,
Sotiris