The hood of a 1991 oldsmobile ninety will not open

Unplug headlight connectors. With switch on, test for voltage going to connectors. If there's voltage then headlights are burned out. If no voltage to connectors, check headlight fuse. If fuse is good than its likely the headlight switch on the dash/steering column that's causing the issue.

Latch Spring Broken or latch cable broken.

It is. Here's a link where you can buy one, and instructions on how to program it. http://www.ekeylessremotes.com/categories/oldsmobile-remotes/1991/ninety-eight.html

its located right behind the pass side tire on the inner side of the frame underneath the vechicle

It depends on your area. You can replace the ignition switch portion yourself. However the key lock has a chip on it that tells your cars computer it is ok to start. The dealer will have to re-program your cars computer to tell it that that key lock cylinder is ok to start the car.

It would be located towards the rear of the vehicle. Most likely either to direct rear of gas tank or front of gas tank.

Check the crank position sensor.(CKP) just dont go replacing parts, check them and verfiy bad.

Probably need to take the grille out to get to the latch.

have you checked for that relays and regulator?

Here is the solution to your problem in details, this is a great write-up to completely bypass the VATS/Passkey system. It's quite easy and saved my car: http://newrockies.ca/vatsbypass