I don't think you can get the remote start after the fact. Maybe an after market one, but not sure about the one you order with the car. While it is dealer installed - it may be that something is also done during manufacturing.and most of the dealer installed options you can order yourself from various places online and install them yourself. some are simple (cargo liner) and some a little more difficult (remote starter). you'll save the installation fee and get the item cheaper.
I would not recommend getting your remote start installed through the dealer. Most if not all dealers contract that out to local electronic chain stores such as circuit city. I would pick a reputable installer and get the starter from them and have them do the install. There are too many things that can be screwed up in a starter install. If you go through your dealer just be sure to ask who they send it to for the install.you absolutely can get and install the remote start after the fact, either the one way or the two way. both are dealer installed options, even when you factory order them. the remote start is simply shipped to the dealer and they do the installation after delivery. if you follow the link i have above you'll see you can order either unit for cars with and without IA. i spoke with partscheap.com and they said while it isn't as easy as installing a floor mat, it is entirely end-user installable (if you are comfortable working with car wiring and such), no programming needed.