3 pin neutral saftey switch check?

I have a good battery and good starter. After replacing the heads on my 2000 Ram van, I have a no start situation.
It worked before now I get a "doink" when I try to start/turn the key. As I said the battery is good x 3 different ones and the starter works on the bench using said batteries. I'm thinking the neutral saftey or connector as the wiring harnesses alongside the drivers side head got a jostled around pretty good in the process.
Electrical situations are not my strong suite. How do I go about checking the switch and the harness?
Thanks