After Effects is a Compositing and Motion graphics application with limited 3D model animation capabilities. The latest versions come with a Light version of Maxon Cinema 4D. The full version has excellent 3D modeling and 3D animation tools and simulations.
Premiere Pro is a Non-Linear editing program designed specifically to edit movies. You can add titles and effects, layer multiple streams of video, apply filters and effects, and perform some limited graphics animations.
If you want to create a 3D maze and animate a 3D model of your robot walking through the maze you need to model the Robot and Maze in a 3D app. All 3D apps have a very steep learning curve. It's impossible for someone with no 3D experience to create a model and animate a walk cycle without some serious study. There is an Open Source, this means free, 3D app that is more than capable to do what you want to do, but it is going to take you a few days to learn how to use the program. It will also take you a few days to learn how to use After Effects. Premiere Pro is probably the easiest program to learn but it is not capable of creating any 3D modeling or animation. If you just want something as simple as Pac Man, then AE, or even Premiere Pro can do the job.
If you are on a budget and, as it sounds, are completely new to this kind of thing, I would suggest that you take a look at Blender as a 3D app. There are plenty of tutorials and a pretty decent community that can get you started. The latest blender demo reel has a great shot of a robot composited in a live action scene at :39
If money is no problem then give the Cinema 4D a try and Basic Workflow to polish up your shots, then use Premiere Pro to edit the shots you create in Cinema 4D and composite and polish in After Effects into a finished movie about your robot. If you have no previous experience expect to spend about a month cranking out your first Robot walking through a maze project.