hi mrwilly123,
To really change the image to greyscale only photoshop can do this.
If you want a greyscale effect that can be done in InDesign.
Create a rectangle the exact size of your image and put it on top of the color image. Fill the rectangle with black.
Open your transparency pallet with the black rectangle still selected. In the blending options of this pallet change 'normal' to 'color'.
It's only an effect so when you are going to a print shop with this file it will still have the color information, resulting in a 4-plate separation (CMYK)
carlow