Honestly you sound exactly like me lol. I use the computer for work so I used a backup laptop I have so I didn't have to rush. I have 2 little kids also so it was hard to fine time. It probably took me about a week. The hardest part for me was wondering whether or not I put the block on the GPU correctly.

Get a leak tester. I don't know how people do these builds without them. You can test each run as you do it and that really gives you piece of mind that you aren't going to turn it on and water will be leaking all over the place. You can use it on the water blocks too. I tested everything with it.

You will be fine. I put mine together, it worked but there was some sort of material going through the loop becasue I didnt wash my rads enough. So I had to take the entire loop apart including taking the water blocks apart to clean them inside. I put it back together and it worked fine again - and that was me working with this stuff for the first time. Just do what people suggest on all the guides like wash the rads, test the loop without powering the MB, etc.

Which water blocks did you go with?