Q: iMac as monitor for Mini mac

I have a mid-2007 iMac which is not performing - i.e. spends a lot of time with spinning ball, we're no longer interested in attempting to restore or reconfigure, it is beyond its useful life on its own. 

My question today is this, "Can my old iMac be used as a display/monitor for a new Mini Mac?".   Along with that question are two follow up questions if it is a possibility to do this.  "Will the contents on old iMac interfere and will the Mini simply look like a whole new computer on my old screen?"

Thanks very much everyone.

Mikey