As noted Asus is offering a GPS Extension Kit for the Asus Tranformer Prime TF201. Does the module has a pass thru USB multipin connector to allow charging from the USB cable or does one have to remove the module to charge the tablet?
No, it does not have any kind of pass through. You cannot charge or dock the Prime when the GPS dongle is plugged in.
Here's a YouTube unboxing that provides a good overview of its physical design.