Most of the parts can be a direct plug-n-play - as most modern manufacturing processes will call for having the least amount of unique parts across a product line - in other words, all Foresters will have basic wiring and connections for all options - but different options may require different connections from the main wiring harness to the item.
Many options on Subaru models can be added at the dealership - as accessories - and so the installation of them will be relatively simple - just added the option and any specific wiring needed for that option.
HOWEVER - there are also specific parts and sensors that may be required them to work properly. An option may be there - but the wiring needs to be added OR the wiring may be there but the option needs to be added.
Now, having said that - another "however". The MFD is controlled by a 3 lever/switch arrangement mounted on the steering wheel. These are the buttons for changing and programming the different screens. As the model you have has just the single screen choice, you may not have that triple lever set up.
Also, there were 3 AC systems (from what I've seen) on the Forester - the manual set-up (like yours) and then 2 automatic systems - single and dual zone. These are the set a temp and forget it type of systems. It can still be manually controlled or left in AUTO or FULL AUTO modes. Dual Zone units allow for temp variations between driver and passenger sides. I think that they're all an electronic unit - not manual sliders and cable hook-ups like older styles - so much of this could be (again) plug n play.
One easy thing to check would be to pull your own MFD and / or center stack HVAC controls and look at the back sides - so you can see the specific plugs and/or connections. Then ask any seller of the units you're interested in to send a picture of their unit so you can compare the connection points. As said, the major wiring will all be there, but there may be shorter option/trim specific wiring and connectors that are needed.
