Windshield Seal Replacement

I'm going to replace my '68 Dart windshield seal. The previous owner made of mess of trying to seal some water leaks. The trim has been removed. I assume replacement is a simple matter of cutting the old seal and prying out the glass, and then installing the new seal and glass using the soapy water and rope method. Correct?

The black mess in the image appears to be Flex-Seal liquid rubber. It doesn't come off easily. Any suggestions as to how to remove it?