That easy, huh? Alright, once my Dingoo gets here (I hate the wait as I order it from a Chinese dealer - a reputable Chinese dealer) I'll toss this on there. And it doesn't matter which LCD mine has, right? It should be universal? And, what if mine turns out to be a HK model? Don't use this then? Sorry for all the questions... but it's the only way I'll learn. I was this way when I was new to the PSP scene, and also when I was new to the DS scene. Now, I'm a great contributor to both.
I'll break the answer down :p
1 - yes, that easy
2 - updating using the "hold down" method doesn't matter, as just the firmware portion is flashed, not the bootloader
3 - it should be universal, yes
4 - if it's a HK dingoo, then you will get a red "unauthorized" screen, and will have to use the firmware flasher/unbricker tool
5 - you can still use this, it's pretty much *impossible* to permenantly break a dingoo by flashing firmware -- I've experimented lots with this, even flashing firmware from other chinachip-based PMPs