Don't feel bad, same thing happened to me my first time, although with much less severe consequences. When I bought my 9.5 Pro (used, ebay, oops!), I cobbled it together, and just left the rx pack sticking out of the radio box (no failsafe). I took the turn at the end of my driveway, and my receiver pack went one way, and my car went wide open the other way.
It crashed THROUGH my neighbor's pipe rail fence, under a travel trailer, and wedged against a jack holding the trailer, where it ran WIDE OPEN until I could jump the fence and shut it off. I figured it was upside down, and would just die, so I didn't rush at first, but it had actually high centered iteslf upright, and would have revved until the engine blew, or it ran out of gas.
This was within 5 minutes of starting my first ever nitro car up to drive. Needless to say, my palms were sweaty, and I was shaking the next couple times I drove my car.
So yeah, lots of us have made stupid mistakes. There is a several page thread on this very topic somewhere, so you can laugh at all of us too.
E-Bay is the best way to find oddball OEM parts on the cheap for massive overhauls. People part out these kits there on a regular basis, you did the right thing.