Ahhh, such excitement
For the centre spotting, mine has a black texta mark in the centre with a white reinformement ring around it to make it easier to see. I think the folded paper trick is the way to go. To get the primary out is simply remove the six screws and out the whole cell comes. Putting it back in can be tricky, the first time I did this I thought the whole tube had gone out of round BUT I hadn't lined up the slot in the cell with the folded seam in the OTA. When that is lined up it almost falls into place. At this stage I wouldn't bother with the secondary, just get your primary spotted and recollimate the scope then enjoy it for a while, its a beauty.
Cheers