1. DSP stereos can be had on eBay for a song and a dance. Just verify that the lights work before you buy. And make sure you get the code or it's useless.
2. The hood latch is right up front, slightly to the right of center, behind the grill. It has a little lever on it. I think it's the only thing there that has a wire connector coming out the bottom. If you mount the switch upside down, the it'll stay open, so the control unit thinks the hood is open. It will never arm the security system if it thinks the hood is open.
3. Batteries to fit a Vig are available anywhere car batteries are sold. As for resetting the stereo, you should have the code. When you first turn it on, the stereo will flash "CODE." Just type in the code and it'll turn on.
No code? Then you'll want to get (or make) a code saver
. It's a simple little thing that lets you plug a 9V battery into the cigarette lighter. This will keep alive all your radio pre-sets, your clock, any stored ECU codes, etc.
Hope this helps.