ROOKIEneedHELP

so if i was going to do the GPS on the bottom (attached to the AC and everything) - i would have to do it myself? or could i pay someone (if i bought this http://www.avojdm.com/advanced_search_result.php?keywords=H6217AG911&x=10&y=16 - would i have to buy a "system" and install it myself?) is it easier and cheaper just to put the GPS/NAVI in this part of the car http://legacygt.com/forums/showthread.php/car-pc-52252.html

so i am a COMPLETE NOOB i have a 2009 subaru legacy (with the AUX port (in the center/armrest consel thing?) i want something like this http://store.mp3car.com/Direct_Fit_Double_Din_LCD_Touch_Screen_for_2005_S_p/dsh-020.htm I dont actually want the LCD monitor part (which i assume is the expensive part) i just want the plastic casing. the most basic NAVI and Music player works i dont care about dvds or anything i want the GPS to be there^^^ NOT here "nav screen bezel" - seen here http://www.subaruparts.com/catalog/?section=903#3077