How do I RAM Preview a section of my whole 10 min video in AE? Please Help!

First mistake you made was editing a 10 minute video in After Effects. This is a highly unusual use of the program. It is designed to work on shots where you are doing things that cannot be done in a non linear editor like Premiere Pro. The most efficient way to work is to do each shot or in some cases, short sequence in AE and then render them and edit the final product in PPro. It sounds like more work but it's faster in the long run.

If you are doing something that can only be done in AE then break each sentence of phrase up into a single comp, render the comp and do the final editing in Premiere Pro. I usually give handles (extra frames at the head and tail) so the timing can be fine tuned in your NLE, the sound effects and other enhancements are much faster to work on than they are in AE. If you find you want to change something in the middle of your 10 minute project and you have broken it down into short sequences in AE then it only takes a few minutes to make the changes in these shorter comps and this also saves you a bunch of time.

If you have a 10 minute comp I would strongly suggest that you render the comp to an image sequence so if anything goes wrong you can go back and pick up on the exact frame where things turned ugly. Once you get your image sequence rendered drop that in PPro, or even in AE, make sure the frame rate matches the original comp, and add the audio to render your final product.

These are all newbie mistakes. Please take time to learn how to use the program effectively. Make sure that you take advantage of the training available on Adobe TV and on the AE product landing page.