Ratchet with a 10mm and 15mm sockets?, or adjustable wrench, and a standard cable tie just in case.
The kit from hervey has all the parts you need, two nitrile o rings and a fresh copper washer for good measure.
Easy to do: Remove air filter housing (3x 10mm bolts I think). Use a socket or adjustable wrench (15mm?) to loosen the hex fitting on the rear facing side of the fuel distributor, passenger side. Carefully slide out the assembly. Do not allow the center pin to touch the FD as you withdraw it or you will ground out the detonator and blow up the fuel tank. Just kidding. That only happens on Ford Pintos and cars where Lucas did the fuel system too.
There are 3 major parts, the main valve assembly you unscrewed, a spring, and an inner cylinder that goes on the spring that likely got stuck inside the opening. If the spring is the last part to come out at first the inner cylinder is lightly stuck inside there. To get it out I just inserted the end of a cable tie, put a little sideways pressure on it and pulled it right out. Replace the two O rings and the copper washer with the new ones, put it all back together and tighten it up. I think it would be tough to cross thread when re installing, but as always be careful and start it by hand first. Run the car to check for leaks before installing the air filter box again.
5 minutes or less.
Photo reference here:
http://www.specialtauto.com/delorean...injection.html
See 3 photos 80% of the way down the page under the heading "Here is where the Hot Start 2 kit goes in the distributor"
I tried to find my own o-rings for this fix 3 years ago, the ones I found were close, but not perfect obviously, one of mine ripped in half and destroyed itself - just get them from John. He's been kind enough to post the photos so let him have the $3.50.