So last night, I basically got things setup and learned a few lessons. The first one is that the AppEngine environment is not your typical PHP web environment. I was trying to build out a login part, using the lessons I learned from OAuth and Google's own PHP API and it wouldn't work because curl isn't available in the environment. The PHP AppEngine environment has its own fetch content by URL, but that means the Google OAuth library wouldn't work and I would need to look elsewhere. Fortunately, AppEngine has a User library that you can tap into. Even more, you can specify in the app.yaml file to protect certain places of your website and it will take care of that for you, which simplifies a lot of what I dealt with previously.
Anyway, the main lesson here is that things are different and what I have used in the past may not work. I was able to get CodeIgniter working in the environment, but I figure I may run into other problems when I try to use some CodeIgniter libraries (i.e. the file Uploader class) and it runs into the environment limitations.