I'm about to pursue shooting a short film. Most of the film will be in black and white. Around the end of the film, I need an effect that will be able to sweep away or dissolve the black and white from the footage or environment and turn the environment back into color again. Are there any tools in After Effects CS5 that can help me achieve this or do I need to use a different program?
Did you shoot in color? If so, how are you converting to black and white? Just using the Black & White effect? Whatever technique you use, you can just disable that effect for the part that you want to be color again. Since you describe a "sweep" or "dissolve", you can probably just use a wipe transition on an adjustment layer.
Your description is far too vague for any deeper explanations. Could be some simple cross fade, could be fancy particle dissolves, could be selective coloring à la "Pleasantville". Depending on which one, the amount of work will differ, but all can be done in AE, perhaps sometimes requiring a plug-in here and there....