I installed mine into an existing vent assy. Here is more info on my installation. http://forums.tdiclub.com/showthread.php?t=364533
I did not find it to be a PITA to install. My vent came out quite easily. The trick is (in my case, anyway) to use the right tool and I also did not follow the instructions exactly. The instructions call for prying it out from the bottom, but I found it to be easier to pry it out from the left side. This way I could pry with the trim removal tool while also pushing it out from the back through the fuse box access on the end of the dashboard. Mine just popped right out. Maybe I just got lucky or maybe yours was tighter or something.
The display covers about half of the vent, so I would assume that it cuts the flow about in half. That said, there is no reason why the display has to be mounted in the vent. It looks OEM when installed there, but the display could (in theory) be mounted anywhere the wire will reach to - like at the bottom of the instrument panel or somewhere else.
Looks nice...I was considering this then I calculated shipping from USA...a lot of money for me...It works great, looks great, and it's easy to install. I love mine! Just get it. After getting an idea about the boost, the best thing for me has been monitoring EGT to see the regens.
Here's mine (reading coolant temperature in my driveway)
It's a US company, I think they're in Ohio, so I suspect there is no way around the conversion from the dollar. The only way might be finding one used from someone in Canada, but that's probably not very likely. You could try calling the owner to see if maybe he'd give you a break. He was nice to me one time when I called about swapping for the newer version with white numbers. He was still charging a fee, but it seemed reasonable. Maybe he'd give you a bit of discount to make up for the conversion.