LCD/LEDs not working, worth replacing?

Okay, before I start, I realized this question might not have a 100% full-proof answer. I'll provide as much detail of the phone as I can.

I bought a broken Galaxy Note II a couple days ago for $20 because it had a broken LCD and a badly cracked digitizer. I thought that at best I would have a fully working phone after replacing the $130-ish LCD, and at worst I would lose $20 (if there was other problems with the phone that were not fixable.) When I went home and tried to charge it, none of the LEDs would turn on and when I connected it to my PC it wouldn't be recognized at all. Basically my question is, if the LCD on a Note II was broken, would there be something stopping the entire phone from starting up and being recognized by a computer? And also, if the LCD was broken bad enough, could that cause the LEDs to stop working?

I just don't want to order the LCD then have to return it if the logic board is fried or something.

Thanks in advance for any help! :)