You can replace the existing AP card in the MBP CD with an upgrade card for the Mac Pro. They are available from PowerMaxx for $49.00 and take about 30 minutes to install, and are a direct replacement in the sense that they have the same number of antenna jacks and the mounting is the same.
You get the 802.11n enabler with the upgrade kit, so you don't need any additional software.
Check out the
details on the accelerate your Mac Web site.
I did it to mine and it was a great upgrade for the money. I took advantage of having the case open to put a faster hard drive in as well.
MD