All you need is an installation kit for your car. You can get one at just about any part store.
yes any after market stereo will fit as long as you got the adapter antenna and the stereo adapter and a stereo connector wiring adapter
http://www.modifiedlife.com/1993-pontiac-bonneville-car-stereo-wiring-schematic/
buy new one
MAYBE WAL-MART IF NOT A STEREO INSTALL SHOP
I hate to admit I searched this topic before noticing the "hr" and "mn" buttons on the bottom right of the stereo console (1998 Pontiac grand prix...stereo with equalizer built in). just press the buttons to adjust the time (with the stereo turned off).
It is right above the stereo console.
i dont know . you gotta figure out how to do it yourself.
No. Its 1.5 DIN
Yes, with trimming of bezel they will fit.
http://www.modifiedlife.com/1995-pontiac-bonneville-car-radio-wire-diagram/
there are a number of stereo wires but if you are installing a new stereo, it is worth buying the installation kit.it comes with a harness that will match all wires.
If it is not a factory stereo, you will need a GM class2 data bus interface device in order to keep other car devices active.