Duce,
The clearance between the thrust plate and aluminum gear should only be .001" to .005". so you've got WAY too much free-play, there.
If the cam's OK, you will still have to remove it, put the new gear on, then reinstall it. Make sure your key is in good shape. I wouldn't even attempt to install a new gear with the cam in the engine, you could dislodge the plug at the rear of the cam.
I've always put the new aluminum gear in boiling water until it was hot. 5 minutes should do it. I install the thrust plate on the cam and put a .002" feeler gauge between the thrust plate and new gear and push the gear right on. If your cam's warm to the touch, putting it in the fridge for a while may help.
