All good advice ... not sure whether I can offer any further advice that's of any help, but being the sort of person I am (wont to giving needless advice), I'll try anyway
Really good engineers and craftsmen have a motto of "measure twice, cut once". To transpose the advice to this, I'd suggest reading instructions to the point where you almost have them memorised before actually starting work. Merely following step-by-step instructions will often find you coming up against a step which makes entirely clear the confusion you inevitably found on an earlier one and normally meant you did the wrong thing. Basically "read ALL the instructions twice; follow them only once", because you'll be following them correctly that way
Finally, anything you're not certain about - no matter how daft you feel - ask in these forums for help. Quite frankly, it's better to look a numpty than it is to blow your new computer, which is incidentally pretty difficult if you don't do anything stupid