No, the top is plastic. Putty knife, kitchen knife, just be slow and careful. If this is on a mobo inside the case, you should have the mobo on a well lit comfortable surface already..... Out of the case.
Take your time. If it's Tpaste it could be very hard and almost like glue.
No, I didn't say mix them. The first part of Artic clean is a pretty powerful natural solvent. Goop off is stronger. So if the first part of AC didn't work, move up the food chain.
So scrape, etc, just do it, use the goop off with qtips and let soak on the top, then use qtips to clean it off etc. Then Artic clean it.
It's ahrd to explain from 1000 miles. Maybe a few properly sized GOOD pics would be nice.