First of all a 19" monitor is friggin' huge in a vehicle. I suggest making a template and insure fitment before you commit to a purchase.
Second, you need an adapter. Here is one for US$120: http://www.impactacoustics.com/produ...ite+to+vga1%29
Thirs, as far as power, it realy depends on the monitor. If it has a power brick type of electric cord, you could likely us a regulator for it. If it has just a power cord, then you're going to need an inverter to power it. It all depends ont he power specifications of the monitor.
So tell us your plans for putting a computer in your ride. After all, that's what we're all about here.