Central locking vacuum pump?
 

I have a chance to buy a 2001 A4 for $700 but it needs a central locking vacuum pump...? Is there a cheaper way to fix this? Does the part have to be from an Audi or does any other car have the same part? And then once installed, do I absolutely have to take it to the dealer to reprogram it? Is this even a good deal? Please answer me asap because I don't want to lose out on the deal!
Thanks!
Amy