Those little bluetooth doodads that plug into a USB port and can be bought for less than $10 generally work fine with Macs, so unless you got a *really* good price on that service part I'm not sure why it'd be worth bothering. Saves a port, I guess.

Internal Bluetooth is almost *always* "electrically" USB unless the functionality is tacked onto another device. (There *may* be combo bluetooth/802.11 modules in some laptops connected via mini-PCI/PCIe but I haven't actually seen one.) There was an amusing problem we were having with Dell D600 laptops some years ago where users were complaining about their computer randomly beeping and telling them it'd found a "new USB device". Turned out that Dell had shoddily designed the laptop housing such that the Bluetooth module, which plugged into a fragile little connector on the motherboard beneath the palmrest, would flex back and forth enough to crack the solder under the plug. I personally cracked open several laptops and yanked out the Bluetooth board (usually the connector would come out with it) in order to quiet the complaining while the company waited for Dell to recall the defective machines. :^b