Howdy Ttocs1980 and welcome to the forum.
That's in fine general condition. I can tell you the height adjustment lever and plastic detents on the body side looks to be original. As you pointed out, the spring steel at the base of the lever stem has completely broken on one side, and as a result, is not sitting in the slots squarely and is causing difficulty to operate and probably can't hold a height position. Corrosion over time is the culprit.
It looks like the entire rear axle will have to be replaced unfortunately, necessitating extensive dismantling.
That may include the gearbox.
Very unfortunate that component has failed.
AS for the handles, you may have to try and work around the cable as it will be a hassle reattaching the lever. The self propelled system can make these more complicated to do repairs, hence why some people choose to remove it altogether and convert it to a push only mower.
