Good approach to leak testing, nice and sensible for your first time is good. A tip for the leak testing is to place kitchen roll or something similar under all your joins, it makes it easier to see a slow leak.
General tips:
Go with a "measure twice, cut once" mentality.
Read up and put in the leg work, ask for advice when you've got a rough plan already, that way people on here can give you anymore pointers. Think of it this way: it might be easier to just ask someone one here to spec you a loop but if it all goes wrong (most likely never but still) it's better to have a good understanding of the stuff.
Ask why you want water. For me it was keeping a reasonable overclock but nice and quiet, for some it's bling factor, for others it's extreme overclocking. If it's "just cus" then I'd stay stick to air.
Don't skimp, cheap water is still usually several times the cost of good air cooling but with more risk and no benefit. Expect to pay £100-£150 for a reasonable CPU only loop.
7/16" Tubing on 1/2" Barbs.
Laing DDC pumps.
I hope this helps, I'm sure the pros will dive in shortly to give you some more indepth advice, this is just a short list of things that will usually get mentioned.
If you do decide water is the way forward then have fun with it, if you get the bug it will be an expensive but rewarding addition to building any PC.