Well, mostly.
I figured out the plumbing (and it wasn't the way I thought). I am satisfied now I could survive a power outage with dry feet.
More importantly, I'm not so intimidated by it any more.
I got the wiring tacked up nicely. I changed out 10% of the water and vaccumed the gravol. I moved the live rocks from the sump in to the tank (tried to create interesting caves etc for the gang... they seem to like it), and most importantly, I got the protein skimmer installed! It seems to work great, but it is frothing out the top which I figure it shouldn't do. I tried adjusting the water level with the pipe at the side, as I was instructed, but it's still frothing. I think I might have too much water in the sump, but taking some water out won't work as the skimmer isn't in the lowest point. I have to change the partition wall, I think. But does it matter if it foams out the top?
I didn't get the second heater installed, but we'd all had enough for one day.
Thanks everyone for your help!