The SS gizmo should have a nice screen in the bottom of it. It attaches to the keg with what is called a 2" sanitary clamp..aka Tri Clamp in some jurisdictions. It gets obvously once a person get a hand on it.

Last time I looked over there the sign say they was out o stock on those things. Did that get some in?

Also if you look down in the keg you should see a inner ring which held in the guts you took out. That needs to come out. If not it choke you down at that spot. All kinds of exotic theories on how best to get it out. My welder say he can scrape it off in 30 seconds with a carbide file. Dremel tool might take a week lol.

You can also buy the kit a chunk at a time if you want to save a little cash. For example you can get the clamp..the SS gizmo and the cheesy o ring from Brewhaus..then only leave you industrious to track down your own copper. I was fortunate to hit it at the first old timey type hardware store I hit. Now they proud of it..but they got it. Twenty bucks and some change. Course I had to buy two so to have a backup..lol. Got expensive.