Help! Changing antenna

I searched the FAQ's and didn't get any matches, so if I'm repeating a question, my apologies.

I can't get the old antenna off my 1990 Integra. It's a power antenna that got vandalized, so I'm replacing it, but I can't seem to figure out how to get the old mounting off the outside. The motor is unbolted from the body, but it won't come out because of the mounting on the outside of the car. Anyone able to help me with this?

I took out my stock antenna assembly from my 95 teg. You have to unbolt it like you said, and then i just unscrewed the part on the outside. It was hard at first, you may need some vice grips or something. I'm not sure if its much different on a 90.