Prior to paying someone to it's worth the time to look into how the unlocking of the DME to upload the tune is done as things have become more refine where the unlock can be done in the car's OBD port vs having to manually open the DME under the intake manifold.
For the stage one you can for the most part run stock though be mindful of the plastic charge pipe as more boost pressure flowing through might bring to light the reason why many of us upgrade that weak point.
My two cents would be for BM3 having been on the platform for a while like many guys here but of course the choice is yours so I'd say read into it and see if it fits the bill as the tune you'd like to run.
https://www.protuningfreaks.com/coll...428i-520i-528i