Working!
Success!

I used a combination of zerf's ADB instructions and luniz7's suggestions and I got it working!
What you're going to need:
WinRAR
"Droid Incredible Official Boot Animation" from this thread:
http://forum.xda-developers.com/showthread.php?t=759691
1. Unzip the DROIDINC_Boot and then unzip the "bootanimation" file to your Desktop. There should be three files, and folder labeled "android," another labeled "VZW" and a file named "desc"
2. Inside the "android" folder, replace the "HTC Quietly Brilliant" image with the 480x800 png of your choice and give it the EXACT SAME NAME:
"wvga_htc_bootup_android_104f_15fps_005spf"
No changes need to be made to either the "VZW" folder or the "desc" file
3. Somewhere on your computer (I did it in Documents), right click, go to the "New" menu, and click "WinRAR ZIP Archive" - make sure it's "ZIP archive" and not just "archive" (first is .zip, second .rar). Name it "bootanimation"
4. Double click on the bootanimation.zip you just created to open WinRAR. It will show you the contents of the zip folder you just created. It's empty - but we're going to change that
5. In the upper left corner you'll see an image of a bundle of books tied together with "Add" underneath. Click this, and navigate to the desktop where you unzipped with original "bootanimation" (now with your custom png). Click on the
"android" folder and "OK." IMPORTANT! Before you click "OK" the second time, be sure to change the "Compression Method" (in the bottom left corner) from "Normal" to "Store." Alright, now you can click OK
6. Repeat step 5 for the "VZW" folder and "desc" file
7. When finished, simply close WinRAR
8. Move the "bootanimation.zip" file you just finished editing to your "tools" folder in your Android SDK
9. Follow zerf's ADB instructions (earlier in this thread) and you're good to go!
As proof, I've uploaded my modified bootanimation with the "unrevoked" splash image in place of "HTC Quietly Brilliant." Hope this helps!
- Zoon0n