What is my Logic board reference number?

Following damage to my macbook (13-inch late 2009)

2.26GHz Intel Core 2 Duo

8GB 1067MHz DDR3

NVIDIA GeForce 9400M 256 MB

Serial number: W90054828PW

I have decided to replace the logic board with a 2nd hand one. However, there seem to be two reference numbers for the same model computer:

1) 820-2567-A 661-5395

2) 820-2883-A P7550

Will they both be compatible with my computer?

Is there likely to be much difference?

How do I find the reference number of my original?

Any comments gratefully received. Thanks.