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If the wall you are dealing with has electrical and plumbing then you need a general contractor, who may sub out some parts of the job as needed to get the right specialties.

If it's just the wall w/ no wiring or plumbing then generally you need a carpenter and a finish carpenter or someone who does both.

A Heating, Ventilation, Refrigeration, and Air Conditioning (HVAC) technician, should be able to handle the vents. If there's electrical involved, you'll need an Electrician for that portion of the work. Though some HVAC companies may be able to handle the whole job.

If you don't want to dish out for an HVAC tech, you could likely handle it yourself with the purchase of a few hand tools. Specifically, you'll want a set of aviation snips (left, right, and straight), and a 5 blade crimping tool. Duct seal mastics are all the rage, though a quality foil tape should work just fine.

If that doesn't appeal to you either, any local "handyman" should be able to do the vent work. Just make sure the person is licensed, insured, and registered with the Better Business Bureau® or some other similar organization.