How hard is gregtech to get into for a complete beginner?
It's not that it's difficult to get into - you won't have to be using college-level calculus, for instance.
The hard part about GregTech is that everything takes more materials to make... so you need to mine more materials... in the end, the most valuable commodity in GregTech is
time.
Just a for-instance... GregTech makes one wood block worth 2 wood planks (not 4 like in vanilla), and it makes two wood planks worth 2 wood sticks (instead of 4). That should give you a good idea of what you'll be dealing with right there. Of course, there is a good solution - the saw. Make a saw and you will indeed get 4 planks per wood and 4 sticks per 2 planks... but you need to take the extra step of crafting a saw, keeping it handy, putting it into the crafting table every time you make planks or sticks... see what I mean?
Time. You'll need plenty of it, beginning with exploring for the ore veins that are few and far between and very hard to find.
I think I just gave up on the InfiTech 2 modpack with GregTech in it. I have plenty of time to play, and it's still not enough. I think what I might do is start a creative world, just to be able to actually play instead of spending all my time exploring and mining and dreaming of the stuff I'll build someday.