The only thing different on an X5 brake controller install - vs. most other vehicles - is where you pick up the brake signal. This signal tells the controller when you are stepping on the brake. You don't NEED any OEM parts, but you can use an OEM pin if you want to plug into the connector instead of tapping into the brake signal wire. (either way is fine). On most vehicles you tap into this signal at the brake pedal. On the X5 you tap into this signal at the Light Control Module in the passenger footwell area.

If you take the pin out I posted to any competent installer, they will be able to install your controller no problem.

FWIW - Having installed the hitch myself, I can tell you that the install will go a lot faster if you select a shop that has done an X5 OEM hitch before.

Happy trails!