Ahh, a fellow yankees fan..welcome 
to put the background on the unit, the picture has to have a size of 800x480. You can check this by going into MS paint, load the picture up and click Image
Attributes. If the number in pixels isnt 800x480, it has to be modified to that size. after that, Create a folder titled "Pictures" on a usb Flash drive or an SD card and store the picture in there. insert the usb drive or sd card into the unit, and goto settings
system settings
splash screen, and import from _____. Press OK
To put the unit where the the screen is, first make sure the screen size is 7"x4". If it is, it's as simple as opening the dash up removing the screen and making brackets to hold the unit. If not, it's gets more involved with either cutting away some of the panel, or creating a trim ring.