A friend of mine has this done to his Mk4 and end result is a nice fit which still looks oem. so i cant imagine itll be that difficult. Ive been considering this too because the space is pretty much perfect.

As for those Pioneer units, my Brother has one and they are one good quality unit. Eclipse also make a good all in one double din screen that my old man got just a few weeks ago. A little simpler to use imo.

Keep us Posted on how u go

Jono