Hi "And" no probs mate. Ok it might be an idea to say where you live, some of the folks on here are more than willing to help out a fellow biker, they can usually be bribed with tea and biscuits.
I'm in Gloucestershire so no real use to you but someone might be nearer and willing to help out. I know we have a couple of lads down in Brighton area so they could be persuaded to help I'm sure. (read your intro post) to be honest there are 2 ways to go, 1 buy the cheapest set of cogs and chain you can find and just bung them on till you know more, that way even if you fuck up it won't cost to much, 2 Buy the very best you can afford and fit them exactly as it says in the manual or even go to your local bike shop and get them to do it, the advantage of that is that you know it will have been done right and can take it back if it all goes tit's up. Just some suggestions for now as the longer your into bikes the more you will learn and be able to do yourself, good luck mate whatever you decide.