Couple of details
Yes, many people on here have done the install themselves ... I have not. It doesn't appear to be that difficult but there are a few things to know.
Do you have a key to start the car, or do you have the keyless start system (push button)?
As for your questions. Assuming you don't have the push-button, you will get an additional FOB for your remote start purposes. The FOB is better than previous years simply because it is 2-way and will let you know when the car is started. Nice. Also, the range is awesome so far.
There is a downside to the OEM remote start. The design implements a "safety feature" that will shut down the engine when ANY door is opened ... no matter how it is opened. So, if you are used to using remote start, opening the door, getting in the car, putting the key in and pressing the brake and driving away ... that is no more. The car shuts off when you open the door and you have to restart it with the key. There are a number of posts on how to bypass the door switches so the car doesn't know the door is opened, but I am not going to do that.
Also, the installation will require Dealer programming for the keys/fobs immobilizers. I don't know how much that costs, but I would assume anywhere between $45 and $90.
If you have a CVT with turn start only, then this is your installation guide:
http://techinfo.subaru.com/proxy/72581/pdf/072581-H001SSG400FM5T-SRESIxIENFR20130527.pdf
If you have push-button start:
http://techinfo.subaru.com/proxy/72125/pdf/072125-H001SSG8002014ForesterP-SRESIxIENFRRev1.2.pdf