I was curious of the same thing and did a photoshop overlay of two macbook air logic board photos, one for the nvidia board and the other one for the intel board and they seem to have the same connectors and the same screw holes. This guarantees nothing, but you would at least have to get the following for the nvidia one:
* Port Hatch Assembly 661-5073
* Macbook air hard drive bracket and cable (for a SATA hdd)
* 5mm, 1.8" SATA LIF HDD or SSD (runcore is coming up with 256GB ones quite soon)
Doing the math looks like this:
Logic Board 2.13 GHz- $800
Port hatch - $45
Hard Drive cable - $40
SSD - $500
----------------------------
Grand Total: ~$1400
Why not simply buy a new one and give your current Air to someone else? On the Apple Store you have a refurbished MBA 2.13 GHz with 128GB SSD at $1549. It comes with warranty and everything. In almost the same money you get a second MBA.