Ok let's start over...
This is the link to the version I have. If you download that, it should work the way I was explaining. That is V1.8c, so try that out.
After downloading that, you should be able to just follow the directions I gave (following the picture I provided as well) to correctly install the UI. Or as Profit said, just extract the folder into your MAIN EverQuest II folder.
If there is an upgrade 1.8d that Profit provided as an attachment here, I haven't used it, but I will look for it.
Ok just found it. I will have a look at those files, but it seems to me that you guys downloaded the update-only patch. Download the whole first attachment (ProfiUI1.8d) and try that. Without the core files, the UI won't run correctly.