Given that consumer telephones are inexpensive, the cost of repairing the speaker phone on the 960 (assuming you still have it) is probably not worth it.
Going off of my memory....to program a speed dial you would first press "Program", enter the telephone number you want stored and then press the one of the memory buttons to save the number to. If the number is to be saved on a lower memory position press "Lower" before you press the memory button.
AT&T's telephone product website has a section where user manuals for many AT&T and Lucent branded telephones.
The 960 is no longer listed, but the many of the basic functions are similar to the 922.