I would not try it in the WWAN slot. If you can access the WPAN/BT slot (it was accessible on the E6400 without disassembly) you can give it a go. It won't be supported obviously, but it might work.

I wish there was a WPAN/BT slot on the E6410. I have a WLAN, next it a WWAN slot, and then in the corner by the fan, there is a ENCR slot (which looks like it is the D-instant On slot for flash mem based OS. Thus is my issue: the E6400 and E6410 are pretty close in design, but yet different enough that there in not a slot for the BT/WPAN chip in the E6410. I have seen instructions to install a BT chip, but it is basically disassembling the entire unit to install a factory part. (I wish I ordered with it, and would be beyond this headache.)

It will not work. the 375 bt module is a rectangular and is in a different location on the 6410 which is a complete change from the 370 model in the E6400.

I ended up getting the 375 chip and disassembling the E6410 to install it. I essentially removed the display, and removed some P screws to separate the top/bottom parts of the shell. I pried open the case and then put the chip into (it goes under the E6410 logo)

You don't by chance remember the part # do you. I'm in the same bind and need to order the 375 module for a user and keep getting the runaround by Dell trying to locate it.

I think it took a lot of chasing my tail to find the part and order it. I think I had to call to Dell to order. On my order confirmation, there were a few numbers:
YKMT7 - Assembly,Cable,Bluetooth,RMA. The price was $4.99 with $8 shipping.
I used the instructions here: http://theitguyshelp.com/?p=12
It was not too bad, just a lot of dis-assembly. It depends on your comfort level with removing screws (and grouping by area/size) and unplugging internal modules. It took me about 30 minutes, but I wanted to go slow.