With any grit blasting I would dismantle any bits that will come off plus with powder coating it will go into an oven so that heat will effect sensitive parts.
A cheaper & easier opion would be to chemically remove the paint / rust then prime & top coat with spray Black gloss.
Would say powder coating is good for suspension parts / subframes road springs etc where protection is required - the air box doesn't get effected by road salt etc.
Powdercoating will have to watch the metal clips to secure the 2 halves as they may stick up with paint being thickish.
Best maybe to speak to the company who will powdercoat it first.
