Basic Module
 

Hi All. I have a 525diesel 2001 on a y plate. I had a problem last year when the battery kept draining and found out that it was the blower resister at fault. I had it changed and it was fine untill now and now I am having the same problem with the battery going flat when the car is parked.
I have had a diagnostic check done and now told by BMW that it is the BASIC MODULE that is at fault. part number 61356942042.
The cost for this approx £400 fitted. To save some money I was going to buy a second had module and get it fitted by my local garage at a fraction of the cost.
I was told by BMW that the new module need to be programmed to my car and I just can't plug it in and make it work.
Can someone please tell me if this is true and what other option I have to have this Basic Module sorted other than going to the main dealer.
Any help will be greatly appreciated.
Thank you