All we wanted to do is change our drain from brass to chrome in our fiber glass shower and I'm afaid we have bitten off more than we can chew. The brass drain is glued in with a 2" piece of pvc pipe sticking up in the center. How can we remove the brass drain wtihout damaging the shower or going in through the ceiling? Please help...

"How can we remove the brass drain wtihout damaging the shower or going in through the ceiling?"

You can't! To remove the old drain you must cut the raiser off and remove the retaining nut and pull up. I have put up a shower drain, (see image) for you to see the nut. If it's not too late consider keeping the brass body drain and replace the strainer with a chrome snap in strainer, (see image).
This is the only way you're going to get around opening up the ceiling.
Good luck, Tom