Double DIN stero install questions

[Storm Smith]

So I have a pretty decent double DIN stero with built in blue tooth. Clarion CX501 CD receiver at Crutchfield.com I would like to install it into my 2000 Grand Prix GT without Bose and Onstar. I noticed that while it is the same width, it is literally less than an inch to tall. I was wondering what people who have put Double DIN stereos in did to get them to fit and work right? Like how to cut the plastic holder, what kind of mount to use. I would appreciate what ever info I can get.