Alrighty, all fixed now. Saving ICQCore.dll directly to the ICQ directory through reshack wasn't working too well for some reason.
To completely rid yourself of the ad banners, do the edits above, and then set the dialog box's y coordinate size to 1 + ad box y coordinate.
So for the following ad box line:
CONTROL "", 1070, "{9F9012BA-E55B-11D3-ADE7-0090270D8F00}", 0x50000000, 1, 158, 260, 38
Start by setting the ad box dimensions to 0, 0:
CONTROL "", 1070, "{9F9012BA-E55B-11D3-ADE7-0090270D8F00}", 0x50000000, 1, 158, 0, 0
And then the main dialog box size coordinates (at the top of the script):
2503 DIALOGEX 0, 0, 262, 196
is changed to:
2503 DIALOGEX 0, 0, 262, 159
That's it - all ad windows, including Send, Receive, File Transfer, URL, and all of the wonderful ad boxes to come (a few that I can think of offhand are in File Transfer (during transfer), User Has A Birthday (bastards), and Chat Request) are completely eliminated and cannot be changed by AOL. Also, if you leave the original icqate DLL files in the ICQ directory, AOL is spoofed into thinking that you're receiving the ads anyway.
From here we just need to modify the ICQCore.dll from the various 2000a and 2000b builds and collect them in an archive for download.
Images:
ICQ Send Message
ICQ Incoming Message
ICQ Send URL
ICQ Send File Request
Have fun, and many thanks to those in this thread that have worked on this for the past few days.