this may help

the spring is definately necessary if you want your petc0ck to work correctly.  When you turn the petc0ck handle to the prime (PRI) position, it presses on the spring.  The little tab that is sticking straight down the middle pushes against the "pin" in the vacuum diaphragm and allows fuel to be allowed thru without a vacuum being pulled from the engine.  Without it you will not be able to put the petc0ck into "prime."

As far as getting it back in... have fun.    I made the mistake of pulling it out, too.  It took me about 20 minutes of working and a 3^rd hand to get it in.  I needed 2 screwdrivers, a pair of needle nose pliers, and a hemo-stat.  I also bent it totally out of shape a couple times and had to pull it out and bend it back into shape.

Or you could just buy a new fuel petc0ck...