I think your talking about the upper strut mount and yes, if you have play in it, it will need to be replaced. I just replaced mine and the upper for each side was about $45 each if I remember right ? I could be wrong, I replaced everything in the front-end when I put the big brakes on. How many miles on the car ? I'm assuming if both of them are making noise you must have quite a-bit of miles on the vehicle. If it's just one side you probably hit something pretty hard to damage the upper strut mount and should have the front suspension checked out completely.
Oh yea, it won't be cheap to replace those items...
Hope this helps.....