After removing the bottom of the Wind's case, I found the OEM card next to the VGA-out port. Removing it required disconnecting two antenna leads and one screw. The new card is a bit longer than the original card, so installation required rerouting the antenna leads but was otherwise the same as if I'd replaced it with another RTL8187.
To get the Intel card recognized in Windows I had to manually install a driver from Intel's website. (I downloaded it on my Mac and sneakernetted it to the Wind on a USB stick.) With the driver installed, Windows Wireless Zero Configuration was able to see a pile of WiFi networks and after I reentered my WPA2 key, I got onto my WLAN.
Getting the card running under Ubuntu 8.10 was actually simpler. From the Intel Wireless WiFi Link driver site:
Note: The iwlwifi driver has been merged into mainline kernel since 2.6.24. If you are using kernels after this release, please use the intree (drivers/net/wireless/iwlwifi) driver directly. After 2.6.26 the intree driver iwlagn also supports the new 5100BG, 5100ABG, 5100AGN, 5300AGN and 5350AGN series hardwares.
The RTL8187 lacks similar support, so every time I upgraded the kernel I'd have to upgrade the wifi card driver. That's no longer a problem.
Incidentally, the Technician's Pocket Screwdriver from Countycomm is perfect for dealing with the screws on the Wind.