A 1978 "should" be the new style ejector assembly.
To disassemble:
FIRST, drop three EMPTY cases in the chambers to support the ejector.
The ejector rod is RIGHT hand threads. Looking end on at the rod, you unscrew it by turning COUNTERCLOCKWISE.
Since the rod is broken and you have nothing to loose, grip the rod as close to the cylinder as you can with a set of Vise-Grips, then just unscrew it...RIGHT HAND THREADS.
Here's an exploded view of the Python so you'll know what's inside.
http://www.brownells.com/aspx/ns/schematics/schemmfg.aspx?schemid=149&m=3&mn=Colt®&model=Python+
Basically, once you unscrew the rod you can pull the crane forward and out of the cylinder.
The ejector will come out the rear.
All that's left is the ejector rod bushing.
The ejector spring is a captive part held in by a threaded bushing in the crane.
There's no need to remove it.
To reassemble:
Put the ejector in the cylinder and put in the three EMPTY cases.
Put the ejector rod bushing on the ejector rod LARGE END FORWARD.
Put the crane in the cylinder.
Put the ejector rod in the front of the crane and tighten hand snug.
To tighten in place, put the rod head in a PADDED vise and rotate the cylinder to tighten the rod down.
DON'T BEND THE ROD.
You want it tight, but DO NOT STRIP THE THREADS.
You can put a TINY drop of BLUE Loctite or fingernail polish on the threads of the ejector rod to prevent it from unscrewing.
BE CAREFUL, botch any of this and you'll be in the deep stuff.
You can buy new rods, but ejectors are HAND FITTED at the factory and they DO NOT "drop in".
Strip an ejector and you better hope Colt can supply and fit a new one, because your local gunsmith can't.