[eluser]sjmiller85[/eluser]
I'm currently working on porting over an app to CI. The best advice I can give is to just start over. You should be able to maintain your views (your .html files) and can easily port them, as well as your database but in general, when it comes to the PHP, you are going to have to inevitably start over. CI handles almost everything different than your traditional PHP programming experiences.
Definitely read through the above links that maesk provided, and as you start to develop stuff, read through the controllers guides in the /user_guides link (it's also provided in your download) where it pertains to what you want to do (ie display forms, database queries, etc...) and read through it entirely before you start. There's a lot things that will drastically change, but once you get in a rhythm, you'll notice that so much of it makes sense, and will definitely help in the long run with conserving time.
