04 X5 Key replacement?

[15x]

I recently had to replace my Engine control module, it was $1255 from dealership so I bought a used one from Pam's Auto in St.Cloud, it came with the key & Immobilizer (Small box mounted by drivers foot) of course the new key doesn't fit my ignition but the car will start & run as long as I have both keys together.
Can I go to the dealership to reprogram my old key to match the new ECM etc...?

Thanks