Draw a wide line (say30 pixels) around what you want to save in a color that is not used in your photo in another layer. Use the magic wand to select that line, Use the lasso to select the rest of the print you wish to make black and white. Save the selection, remove the new layer. Reload the selection. change it to grey scale.
i gotta run to get groceries, I'll be back later. Let me know if that's thorough enough or not.
They have some basic tutorials on the page here, just kinda click on what you would like to do and there is a walkthrough with easy steps to follow. If that doesn't do it I have a photoshop training CD i can send you. Just PM me and I can upload it to www.yousendit.com and you can burn it to CD and use it
theres a tool called wand, looks like one, any way that will pick specific color, at top after you select it there is an tolerance box play around with that and you can increase or decrese the sensitivity of how much range it will select . also you can hit shift and select more or deselect if you went to far.. I look around for a tut fer ya! L8ter here the link good luck tutorial
You don't have to invert it really. Just create the layer and select monotone then use black as the primary and white as secondary color. Then just use the brush tool to turn whatever you want back to color and leave the reast black and white