I suggest you try something smaller, because you've said so yourself, you're a newbie to electronics. My concern is that you going to build an amp that has a big power supply, lots of transistors, huge heatsinks and so on and so forth. All these elements will present problems (and lots of them) to the inexperienced DIY'er. I suggest you start with a more modest design, don't reach for the uiltimate goal straightaway.
I'm saying this to prevent you from frustration and disappointment, and my comments are certainly not meant to be degrading. If you still want to go ahead with an 1.2, go for it, but beware of a bumpy ride....
Xcel