Its an ex-taxi. I've been driving it for an indie film about 3 weeks now, at night, put about 500 miles on it. Its been running fine, leaks a bit of fluid after being driven, but its water, not oil or gas or whatever. About 2 weeks ago the 'check engine' light came on but there didn't seem to be any change in it so we said screw it and kept driving it, no problems until...Its been sitting for 10 days, maybe 2 weeks. We went to drive it and it won't start, won't kick over, not even w/ jumper cables. nothing.The lights still work, interior and exterior, the meter lights up too, it's never overheated, its never sounded anything but Ford V8 Crown Vic awesome, no deceleration or loss of power, even after the light came on, but now its saying sorry pal, no dice and won't start. We're shooting this thing on GoPros and a Top Ramen budget, the car cost a grand and I really want to avoid putting a bunch of money into it. We have like 2 scenes left to shoot for the love of sweet Christ, TWO! I'm thinking (praying is more like it) that its just the alternator, maybe the starter, since when we turn the key it makes ZERO sound whatsoever; no click, no whir-whir-whir, no nothing.
Thanks and any reasonable and sane input would be greatly appreciated.

Speed odometer, power door locks, rear defroster, and speed odometer instrument panel lights are all not working.