How do I service and repair this diverter?

[captaintrav]

On a tight budget, but I'm handy. The diverter leaks both ways, it has a little lever to flip back and forth. Either way, the shower is getting water when you don't want it to, or you're getting lots out of the faucet but not enough pressure from the shower. I tried to pull the stem, but I can't find what's the appropriate way to deal with this sucker:

 

[Basher]

Presumably that whole cover comes off to gain access to the valve?
The knurled ring on the right looks a bit chewed - have you tried that already 🤔

 

[captaintrav]

Found out the diverter valve just pulls out, there was a bung (I don't know what you call it) that I unthreaded already, and then I just made a makeshift puller with a socket, then a washer and tightened down a long screw to pull the valve out.