BT module socket is located under Faraday plate, in left part of logic board, next to telephone modem module.
Getting this antenna kit for BT is PITA (at least in my country).
Like others said: get Airport Extreme card and BT USB dongle, unless you'll have opportunity to get original BT board and antenna kit.
BTW, didn't you think about overclocking this 1.42? It's doing great @1.92 GHz.