Can it be purchased on a site such as ebay and installed? I recently replaced the display in my 1150 and had no problem when I used the instructions downloaded from Dell.
Check out this page from the 1150 Service Manual: Removing/Installing Cards. The section on the wireless card is toward the bottom of the page. You should check to see if you can find antenna wires; if the laptop was not ordered with the wireless card the antenna wires are sometimes missing also.
If you have the antenna wires you can check out the Network section of Drivers and Downloads to see what cards the laptop should support.