It appears that one of the following cards may have been originally installed in your model;
504593-003 Broadcom 4312 802.11b/g (Demi-2) WLAN adapter - Half-size form factor (Most-of-World)
518436-001 802.11B/G/N WLAN HF MiniCard (Medoc) - Most of World implementation
518437-001 802.11A/B/G/N WLAN HF minicard (MD2020) - Most of World implementation
572520-001 Intel Wi-Fi Link 1000 802.11b/g/n WLAN module
Therefore the 518437-001 Atheros 802.11A/B/G/N WLAN HF minicard (MD2020) should work without issue. Use of other card may not work.
If you have any further questions, please don't hesitate to ask.
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