if the inhibitor switch and/or downshift solenoid are not connected, will this prevent the car from firing?

Yes. The purpose of the inhibitor switch is to prevent starting unless the car is in neutral (or 'park' for auto trannies). When I swapped out an auto tranny for a manual (which did not have the inhibitor switch) I had to connect the two switch leads before the car would fire. So the default position of the switch is 'open'. It closes, and completes the circuit, when the tranny is in neutral or park. Connect them together, tape them well and it should fire up.

which ones do you connect together? i see 2 green wires w/ male barrel connectors and 2 white/black wires w/ female barrel connectors

It's been a few years since I did the swap, so I can't remember which are the relevant wires. I'll definitely be able to check for you by the weekend at the latest. I'll send you a PM if this post isn't still on the board.

Connect the w/b wires. The green ones are for the reverse light switch.

Thanks Steve. Saves me a trip under the hood, .

You might also want to connect the two green wires together (if you're changing form an A/T to a M/T) or the reverse lights won't work.

i can't thank you enough sblake. your knowledge of s30's seem to be bottomless